ibmvnic: Move ibmvnic adapter intialization to its own routine

The intialization of the ibmvnic driver with respect to the virtual
server it connects to should be moved to its own routine. This will
alolow the driver to initiate this process from places outside of
the drivers probe routine.

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