This removes <linux/mm.h> from <linux/vmalloc.h>.

This then goes and fixes all of the files (x86 and PPC) which relied on
implicit includes which don't happen anymore.  This also takes
<linux/kdev_t.h> out of fs/mpage.c and puts it into include/linux/bio.h
where it belongs since <linux/bio.h> references 'kdev_t' directly.

A quick summary of the of the added includes:
arch/i386/kernel/microcode.c: needs extern for num_physpages, in linux/mm.h
include/linux/spinlock.h: local_irq* is defined in <asm/system.h> but
this was never directly included.