Make some global functions and variables static.

And remove some useless declarations for local functions, since we just need
to move their definitions ahead.

[jdike@addtoit.com: checkpatch cleanups]
Signed-off-by: NWANG Cong <wangcong@zeuux.org>
Signed-off-by: NJeff Dike <jdike@addtoit.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>