checkpatch: fix unescaped left brace

checkpatch: fix unescaped left brace

There is an unescaped left brace in a regex in OPEN_BRACE check.  This
throws a runtime error when checkpatch is run with --fix flag and the
OPEN_BRACE check is executed.

Fix it by escaping the left brace.

Link: https://lkml.kernel.org/r/20201115202928.81955-1-dwaipayanray1@gmail.com
Fixes: 8d1824780f2f ("checkpatch: add --fix option for a couple OPEN_BRACE misuses")
Signed-off-by: Dwaipayan Ray <dwaipayanray1@gmail.com>
Acked-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>