Fixed -Wunused warnings when building without asymmetric crypto
diff --git a/library/psa_crypto.c b/library/psa_crypto.c
index e26a7ec..e6ef7f7 100644
--- a/library/psa_crypto.c
+++ b/library/psa_crypto.c
@@ -2003,6 +2003,7 @@
 /* Message digests */
 /****************************************************************/
 
+#if defined(MBEDTLS_RSA_C) || defined(MBEDTLS_ECDSA_DETERMINISTIC)
 static const mbedtls_md_info_t *mbedtls_md_info_from_psa( psa_algorithm_t alg )
 {
     switch( alg )
@@ -2043,6 +2044,7 @@
             return( NULL );
     }
 }
+#endif
 
 psa_status_t psa_hash_abort( psa_hash_operation_t *operation )
 {