scsi: ibmvfc: Advertise client support for using hardware channels

Previous patches have plumbed the necessary Sub-CRQ interface and channel
negotiation MADs to fully channelize via hardware backed queues.

Advertise client support via NPIV Login capability IBMVFC_CAN_USE_CHANNELS
when the client bits have MQ enabled via vhost->mq_enabled, or when
channels were already in use during a subsequent NPIV Login. The later is
required because channel support is only renegotiated after a CRQ pair is
broken. Simple NPIV Logout/Logins require the client to continue to
advertise the channel capability until the CRQ pair between the client is
broken.

Link: https://lore.kernel.org/r/20210114203148.246656-14-tyreld@linux.ibm.com


Reviewed-by: Brian King <brking@linux.vnet.ibm.com>
Signed-off-by: Tyrel Datwyler <tyreld@linux.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>