mm/bootmem.c: use include/linux/ headers

Replace asm. headers with linux/headers:

<linux/bug.h>
<linux/io.h>

Signed-off-by: Paul McQuade <paulmcquad@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>