scsi: ibmvfc: Implement channel enquiry and setup commands

New NPIV_ENQUIRY_CHANNEL and NPIV_SETUP_CHANNEL management datagrams (MADs)
were defined in a previous patchset. If the client advertises a desire to
use channels and the partner VIOS is channel capable then the client must
proceed with channel enquiry to determine the maximum number of channels
the VIOS is capable of providing, and registering SubCRQs via channel setup
with the VIOS immediately following NPIV Login. This handshaking should not
be performed for subsequent NPIV Logins unless the CRQ connection has been
reset.

Implement these two new MADs and issue them following a successful NPIV
login where the VIOS has set the SUPPORT_CHANNELS capability bit in the
NPIV Login response.

Link: https://lore.kernel.org/r/20210114203148.246656-13-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>