The context feature of sparse is used with the Linux kernel sources to
check for imbalanced uses of locks.  Document the annotations defined in
include/linux/compiler.h that tell sparse what to expect when a lock is
held on function entry, exit, or both.

Signed-off-by: Ed Cashin <ecashin@coraid.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Acked-by: Christopher Li <sparse@chrisli.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>