ks8842: Replace usage of dev_dbg with netdev_dbg

This patch replaces all usage of dev_dbg with netdev_dbg.

A side effect is that the pointer to the platform device in the adapter
struct can be removed.

Signed-off-by: Richard Röjfors <richard.rojfors@pelagicore.com>
Signed-off-by: David S. Miller <davem@davemloft.net>