scsi: ibmvfc: Make channel allocation generic

With the coming of NVMeoF support the driver will need to also allocate
channels for NVMe. Implement generic channel allocation wrappers that can
be used for both SCSI and NVMeoF protocol setup.

Signed-off-by: Tyrel Datwyler <tyreld@linux.ibm.com>
Link: https://lore.kernel.org/r/20230921225435.3537728-9-tyreld@linux.ibm.com


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