ibmvnic: Add netdev_dbg output for debugging

To ease debugging of the ibmvnic driver add a series of netdev_dbg()
statements to track driver status, especially during initialization,
removal, and resetting of the driver.

Signed-off-by: Nathan Fontenot <nfont@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>