Remove MAYBE_BUILD_BUG_ON

Now BUILD_BUG_ON() can handle optimizable constants, we don't need
MAYBE_BUILD_BUG_ON any more.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

diff --cc include/linux/gfp.h
Simple merge

diff --cc include/linux/kernel.h
Simple merge

diff --cc include/linux/kmemcheck.h
Simple merge

diff --cc include/linux/virtio_config.h
Simple merge