netfilter: xt_osf: Use continue to reduce indentation

Invert logic in test to use continue.

This routine already uses continue, use it a bit more to
minimize > 80 column long lines and unnecessary indentation.

No change in compiled object file.

Other miscellanea:

o Remove trailing whitespace
o Realign arguments to multiline statement

Signed-off-by: Joe Perches <joe@perches.com>
Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>