scsi: ibmvfc: Implement channel queue depth and event buffer accounting

scsi: ibmvfc: Implement channel queue depth and event buffer accounting

Extend ibmvfc_queue, ibmvfc_event, and ibmvfc_event_pool to provide queue
depths for general I/O commands and reserved commands as well as proper
accounting of the free events of each type from the general event
pool. Further, calculate the negotiated max command limit with the VIOS at
NPIV login time as a function of the number of queues times their total
queue depth (general and reserved depths combined).

This does away with the legacy max_request value, and allows the driver to
better manage and track it resources.

Signed-off-by: Tyrel Datwyler <tyreld@linux.ibm.com>
Link: https://lore.kernel.org/r/20230921225435.3537728-3-tyreld@linux.ibm.com
Reviewed-by: Brian King <brking@linux.vnet.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>