checkpatch: remove column limit for checkpatch patches

Currently checkpatch is enforcing an 80 character column
limit. This should not be applied for patches modifying
checkpatch.

Change-Id: I8e8935e633d79a7ee535ce6a90e54447a22d9a91
Signed-off-by: Israel Schlesinger <israels@codeaurora.org>
(cherry picked from commit 4aa1b864119e2d0e49efefcd6dba7349f13c3939)
Signed-off-by: Stepan Moskovchenko <stepanm@codeaurora.org>