checkpatch: suspect indent -- skip over preprocessor, label and blank lines

We should skip over and check the lines which follow preprocessor
statements, labels, and blank lines.  These all have legitimate reasons to
be indented differently.

Signed-off-by: Andy Whitcroft <apw@shadowen.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>