isdn/divert: fix readability damage

Fix up some of the readibility deterioration caused by last year's
ISDN whitespace coding style cleanup.
Note that the checkpatch complaints all apply to the state of the
source before this patch as well, and in many cases even more so.

Signed-off-by: Tilman Schmidt <tilman@imap.cc>
Signed-off-by: David S. Miller <davem@davemloft.net>