Currently the discovery layers within the driver use the SCSI midlayer
host_lock to access node-specific structures. This can contend with the I/O
path and is too coarse of a lock.

Rework the driver so that it uses a lock specific to the remote port node
structure when accessing the structure contents. A few of the changes
brought out spots were some slightly reorganized routines worked better.

Link: https://lore.kernel.org/r/20201115192646.12977-6-james.smart@broadcom.com


Co-developed-by: Dick Kennedy <dick.kennedy@broadcom.com>
Signed-off-by: Dick Kennedy <dick.kennedy@broadcom.com>
Signed-off-by: James Smart <james.smart@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>