svcrpc: fix kfree oops in gss-proxy code

mech_oid.data is an array, not kmalloc()'d memory.

Cc: stable@vger.kernel.org
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>

net/sunrpc/auth_gss/gss_rpc_upcall.c

@@ -328,7 +328,6 @@ void gssp_free_upcall_data(struct gssp_upcall_data *data)
 	kfree(data->in_handle.data);
 	kfree(data->out_handle.data);
 	kfree(data->out_token.data);
-	kfree(data->mech_oid.data);
 	free_svc_cred(&data->creds);
 }