[SCSI] ibmvfc: Better handle other FC initiators

The ibmvfc driver currently always sets the role of all rports
to FC_PORT_ROLE_FCP_TARGET, which is not correct for other initiators.
This can cause problems if other initiators are on the fabric
when we then try to scan the rport for LUNs. Fix this by looking
at the service parameters returned in the PRLI to set the roles
appropriately. Also look at the returned service parameters to
decide whether or not we were actually able to successfully log into
the target.

Signed-off-by: Brian King <brking@linux.vnet.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>