checkpatch: fix up comment checks search to scan the entire block

We are not counting the lines in the block correctly which causes the
comment scan to stop prematurly and thus miss comments which end at the
end of the block.  Fix this up.

Signed-off-by: Andy Whitcroft <apw@shadowen.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>