Rm now-duplicate helper function

Again, the guards are slightly different, let's see in the CI if this
causes any trouble.

Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
diff --git a/library/psa_crypto_rsa.c b/library/psa_crypto_rsa.c
index 19011a4..7d4718d 100644
--- a/library/psa_crypto_rsa.c
+++ b/library/psa_crypto_rsa.c
@@ -543,8 +543,7 @@
                                           mbedtls_rsa_context *rsa )
 {
     psa_algorithm_t hash_alg = PSA_ALG_RSA_OAEP_GET_HASH( alg );
-    const mbedtls_md_info_t *md_info = mbedtls_md_info_from_psa( hash_alg );
-    mbedtls_md_type_t md_alg = mbedtls_md_get_type( md_info );
+    mbedtls_md_type_t md_alg = mbedtls_hash_info_md_from_psa( hash_alg );
 
     return( mbedtls_rsa_set_padding( rsa, MBEDTLS_RSA_PKCS_V21, md_alg ) );
 }