convert print_IPaddr() to %pI4

convert print_IPaddr() to %pI4

Now that our printf functions support the %pI4 modifier like the kernel,
let's drop the inflexible print_IPaddr() function and covert over to the
%pI4 modifier.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
CC: Ben Warren <biggerbadderben@gmail.com>