checkpatch: fix jiffies comparison and others

checkpatch could not distinguish between a variable in a struct named
jiffies and the normal jiffies.

	foo->jiffies

would emit a "Comparing jiffies" arning.

Update the $Compare variable to do a negative look-behind for "-" when
finding a ">" so that a pointer dereference like -> isn't a comparison.

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>