checkpatch: complain about executable files

Complain about files with an executable bit set that are not in a scripts/
directory and are not type .pl, .py, .awk, or .sh

Based on an initial patch from Stephen.

Signed-off-by: Joe Perches <joe@perches.com>
Acked-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>