psa_crypto_rsa: remove PK_WRITE_C in psa_rsa_export_key

Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
diff --git a/library/psa_crypto_rsa.c b/library/psa_crypto_rsa.c
index 0db425f..3ff589d 100644
--- a/library/psa_crypto_rsa.c
+++ b/library/psa_crypto_rsa.c
@@ -172,10 +172,6 @@
                                         size_t data_size,
                                         size_t *data_length)
 {
-/* Currently this is always true due to the fact that build_info.h auto-enables
- * MBEDTLS_PK_WRITE_C whenever both PSA and RSA_C are enabled.
- * However we keep the guard here to emphasize this dependency explicitly. */
-#if defined(MBEDTLS_PK_WRITE_C)
     int ret;
     mbedtls_pk_context pk;
     uint8_t *pos = data + data_size;
@@ -212,14 +208,6 @@
 
     *data_length = ret;
     return PSA_SUCCESS;
-#else
-    (void) type;
-    (void) rsa;
-    (void) data;
-    (void) data_size;
-    (void) data_length;
-    return PSA_ERROR_NOT_SUPPORTED;
-#endif /* MBEDTLS_PK_WRITE_C */
 }
 
 psa_status_t mbedtls_psa_rsa_export_public_key(