checkpatch: suspect code indent must stop at #else/#elif

When we hit and #else or #elif we know we are meeting an alternative piece
of code.  All bets are off on indent if we did not see the open of the
control so stop checking.

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>