pk/psa: use PSA guard for mbedtls_ecc_group_to_psa() and mbedtls_ecc_group_of_psa()

This allows also to:
- removing the dependency on ECP_C for these functions and only rely
  on PSA symbols
- removing extra header inclusing from crypto_extra.h
- return MBEDTLS_PK_USE_PSA_EC_DATA and MBEDTLS_PK_HAVE_ECC_KEYS to
  their original position in pk.h

Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
diff --git a/include/mbedtls/pk.h b/include/mbedtls/pk.h
index ba15447..089333d 100644
--- a/include/mbedtls/pk.h
+++ b/include/mbedtls/pk.h
@@ -40,35 +40,6 @@
 #include "mbedtls/ecdsa.h"
 #endif
 
-/* Internal helper to define which fields in the pk_context structure below
- * should be used for EC keys: legacy ecp_keypair or the raw (PSA friendly)
- * format. It should be noticed that this only affect how data is stored, not
- * which functions are used for various operations. The overall picture looks
- * like this:
- * - if USE_PSA is not defined and ECP_C is then use ecp_keypair data structure
- *   and legacy functions
- * - if USE_PSA is defined and
- *     - if ECP_C then use ecp_keypair structure, convert data to a PSA friendly
- *       format and use PSA functions
- *     - if !ECP_C then use new raw data and PSA functions directly.
- *
- * The main reason for the "intermediate" (USE_PSA + ECP_C) above is that as long
- * as ECP_C is defined mbedtls_pk_ec() gives the user a read/write access to the
- * ecp_keypair structure inside the pk_context so he/she can modify it using
- * ECP functions which are not under PK module's control.
- */
-#if defined(MBEDTLS_USE_PSA_CRYPTO) && defined(PSA_WANT_KEY_TYPE_ECC_PUBLIC_KEY) && \
-    !defined(MBEDTLS_ECP_C)
-#define MBEDTLS_PK_USE_PSA_EC_DATA
-#endif /* MBEDTLS_USE_PSA_CRYPTO && !MBEDTLS_ECP_C */
-
-/* Helper symbol to state that the PK module has support for EC keys. This
- * can either be provided through the legacy ECP solution or through the
- * PSA friendly MBEDTLS_PK_USE_PSA_EC_DATA. */
-#if defined(MBEDTLS_PK_USE_PSA_EC_DATA) || defined(MBEDTLS_ECP_C)
-#define MBEDTLS_PK_HAVE_ECC_KEYS
-#endif /* MBEDTLS_PK_USE_PSA_EC_DATA || MBEDTLS_ECP_C */
-
 #if defined(MBEDTLS_USE_PSA_CRYPTO) || defined(MBEDTLS_PSA_CRYPTO_C)
 #include "psa/crypto.h"
 #endif
@@ -231,6 +202,35 @@
 #define MBEDTLS_PK_CAN_ECDH
 #endif
 
+/* Internal helper to define which fields in the pk_context structure below
+ * should be used for EC keys: legacy ecp_keypair or the raw (PSA friendly)
+ * format. It should be noticed that this only affect how data is stored, not
+ * which functions are used for various operations. The overall picture looks
+ * like this:
+ * - if USE_PSA is not defined and ECP_C is then use ecp_keypair data structure
+ *   and legacy functions
+ * - if USE_PSA is defined and
+ *     - if ECP_C then use ecp_keypair structure, convert data to a PSA friendly
+ *       format and use PSA functions
+ *     - if !ECP_C then use new raw data and PSA functions directly.
+ *
+ * The main reason for the "intermediate" (USE_PSA + ECP_C) above is that as long
+ * as ECP_C is defined mbedtls_pk_ec() gives the user a read/write access to the
+ * ecp_keypair structure inside the pk_context so he/she can modify it using
+ * ECP functions which are not under PK module's control.
+ */
+#if defined(MBEDTLS_USE_PSA_CRYPTO) && defined(PSA_WANT_KEY_TYPE_ECC_PUBLIC_KEY) && \
+    !defined(MBEDTLS_ECP_C)
+#define MBEDTLS_PK_USE_PSA_EC_DATA
+#endif /* MBEDTLS_USE_PSA_CRYPTO && !MBEDTLS_ECP_C */
+
+/* Helper symbol to state that the PK module has support for EC keys. This
+ * can either be provided through the legacy ECP solution or through the
+ * PSA friendly MBEDTLS_PK_USE_PSA_EC_DATA. */
+#if defined(MBEDTLS_PK_USE_PSA_EC_DATA) || defined(MBEDTLS_ECP_C)
+#define MBEDTLS_PK_HAVE_ECC_KEYS
+#endif /* MBEDTLS_PK_USE_PSA_EC_DATA || MBEDTLS_ECP_C */
+
 /**
  * \brief           Types for interfacing with the debug module
  */