psa: Add backwards compatible error codes

Add deprecated error codes to help transition between the previous
version of the PSA Crypto specification and the current one.
diff --git a/include/psa/crypto_extra.h b/include/psa/crypto_extra.h
index 96b478b..86d9954 100644
--- a/include/psa/crypto_extra.h
+++ b/include/psa/crypto_extra.h
@@ -37,6 +37,29 @@
 /* UID for secure storage seed */
 #define PSA_CRYPTO_ITS_RANDOM_SEED_UID 0xFFFFFF52
 
+/*
+ * Deprecated PSA Crypto error code definitions
+ */
+#if !defined(MBEDTLS_DEPRECATED_REMOVED)
+#define PSA_ERROR_UNKNOWN_ERROR \
+    MBEDTLS_DEPRECATED_NUMERIC_CONSTANT( PSA_ERROR_GENERIC_ERROR )
+#endif
+
+#if !defined(MBEDTLS_DEPRECATED_REMOVED)
+#define PSA_ERROR_OCCUPIED_SLOT \
+    MBEDTLS_DEPRECATED_NUMERIC_CONSTANT( PSA_ERROR_ALREADY_EXISTS )
+#endif
+
+#if !defined(MBEDTLS_DEPRECATED_REMOVED)
+#define PSA_ERROR_EMPTY_SLOT \
+    MBEDTLS_DEPRECATED_NUMERIC_CONSTANT( PSA_ERROR_DOES_NOT_EXIST )
+#endif
+
+#if !defined(MBEDTLS_DEPRECATED_REMOVED)
+#define PSA_ERROR_INSUFFICIENT_CAPACITY \
+    MBEDTLS_DEPRECATED_NUMERIC_CONSTANT( PSA_ERROR_INSUFFICIENT_DATA )
+#endif
+
 /**
  * \brief Library deinitialization.
  *