Raw sys_mmap() returns address or error like -ENOMEM.
Don't check MAP_FAILED, check that result is aligned by page.

travis-ci: success for x86/compat: fix error-check for compat mmap()
Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>