fixup: Make the fields of mbedtls_ecp_curve_info public

Remove more places where MBEDTLS_PRIVATE() was used on grp_id, which is now
public.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/include/mbedtls/psa_util.h b/include/mbedtls/psa_util.h
index f6f2e58..6f63545 100644
--- a/include/mbedtls/psa_util.h
+++ b/include/mbedtls/psa_util.h
@@ -369,7 +369,7 @@
     if( curve_info == NULL )
         return( 0 );
     return( PSA_KEY_TYPE_ECC_KEY_PAIR(
-                mbedtls_ecc_group_to_psa( curve_info->MBEDTLS_PRIVATE(grp_id), bits ) ) );
+                mbedtls_ecc_group_to_psa( curve_info->grp_id, bits ) ) );
 }
 #endif /* MBEDTLS_ECP_C */