checkpatch: suggest cleanpatch and cleanfile when appropriate

When we hit types of whitespace which may be fixed by scripts/cleanpatch
and scripts/cleanfile suggest their use in our report.

Suggested-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Signed-off-by: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>