[PATCH] mm/{mmap,nommu}.c: several unexports

I didn't find any possible modular usage in the kernel.

This patch was already ACK'ed by Christoph Hellwig.

Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>