docbook: fix printk of ip address

Use the %pI4 format string instead of %d.%d.%d.%d and NIPQUAD.

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>