checkpatch: improve network block comment test and message

Show the first line of the comment after a line with just /* to better
show where the defective comment style is in the file.

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Git-commit: fdb4bcd6108602097b9a1ebd11f6e61f331c8dce
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Signed-off-by: Stepan Moskovchenko <stepanm@codeaurora.org>