commit 30b11ee9 upstream.

As we got rid of the __KERNEL__ abuse, we can directly
include linux/compiler.h now.
This also allows gcc 5 to build UML.
Reported-by: Hans-Werner Hilse <hwhilse@gmail.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>