checkpatch: allow commit descriptions on separate line from commit id

The general form for commit id and description is

  'Commit <12+hexdigits> ("commit description/subject line")'

but commit logs often have relatively long commit ids and the commit
description emds on the next line like:

  Some explanation as to why commit <12+hexdigits>
  ("commit foo description/subject line") is improved.

Allow this form.

Signed-off-by: Joe Perches <joe@perches.com>
Suggested-by: Joe Lawrence <joe.lawrence@stratus.com>
Tested-by: Joe Lawrence <joe.lawrence@stratus.com>
Suggested-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>