pkwrite: remove unnecessary code duplication

Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
diff --git a/library/pkwrite.c b/library/pkwrite.c
index 8df6394..d684815 100644
--- a/library/pkwrite.c
+++ b/library/pkwrite.c
@@ -404,15 +404,9 @@
 
     grp_id = mbedtls_pk_get_group_id(pk);
     /* privateKeyAlgorithm */
-#if defined(MBEDTLS_PK_USE_PSA_EC_DATA)
     if ((ret = mbedtls_oid_get_oid_by_ec_grp_algid(grp_id, &oid, &oid_len)) != 0) {
         return ret;
     }
-#else /* MBEDTLS_PK_USE_PSA_EC_DATA */
-    if ((ret = mbedtls_oid_get_oid_by_ec_grp_algid(grp_id, &oid, &oid_len)) != 0) {
-        return ret;
-    }
-#endif /* MBEDTLS_PK_USE_PSA_EC_DATA */
     MBEDTLS_ASN1_CHK_ADD(len,
                          mbedtls_asn1_write_algorithm_identifier_ext(p, buf, oid, oid_len, 0, 0));