BACKPORT: checkpatch: special audit for revert commit line

Currently checkpatch.pl does not recognize git's default
commit revert message and will complain about the hash format.
Add special audit for revert commit message line to fix it.

Signed-off-by: Wei Wang <wvw@google.com>
Acked-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Bug: 37158168
Test: checkpatch.pl --patch [diff] and no longer see failure
Change-Id: I65cf9a46874621dd6d5c349d2d3ca3b862d61ba3

scripts/checkpatch.pl

@@ -2162,6 +2162,7 @@ sub process {
 
 # Check for improperly formed commit descriptions
 		if ($in_commit_log &&
+		    $line !~ /^This reverts commit [0-9a-f]{7,40}/ &&
 		    $line =~ /\bcommit\s+[0-9a-f]{5,}/i &&
 		    !($line =~ /\b[Cc]ommit [0-9a-f]{12,40} \("/ ||
 		      ($line =~ /\b[Cc]ommit [0-9a-f]{12,40}\s*$/ &&