checkpatch: test multiple line block comment alignment

Warn when block comments are not aligned on the *

/*
 * block comment, no warning
 */

/*
  * block comment, emit warning
  */

Link: http://lkml.kernel.org/r/edb57bd330adfe024b95ec2a807d4aa7f0c8b112.1472261299.git.joe@perches.com
Signed-off-by: Joe Perches <joe@perches.com>
Reported-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>