This function return value is invariant since 18f3771, so change
its type and remove all dependent checks.
Found by Linux Verification Center (linuxtesting.org) with Svace.
Reported-by: Pavel Nekrasov <p.nekrasov@fobos-nt.ru>
Signed-off-by: Alexander Kuznetsov <kuznetsovam@altlinux.org>
Reviewed-by: Jiri Denemark <jdenemar@redhat.com>