cleanup asm-generic/atomic.h

 - no longer a userspace header
 - remove the unneeded #include <asm/types.h>
 - #else/#endif comments

[akpm@osdl.org: fix arm build]
Signed-off-by: NAdrian Bunk <bunk@stusta.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>