arcnet: Convert BUGMSG and BUGMSG2 to arc_prink and arc_cont

These macros don't actually represent BUG uses but are more commonly
used as logging macros, so use a more kernel style macro.

Convert the BUGMSG from a netdev_ like use to actually use netdev_<level>.

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>