Register driver for threaded interrupts.

By default the driver will attempt I/O completion from interrupt context
(primary handler). Since the driver tracks per reply queue outstanding
I/Os, it will schedule threaded ISR if there are any outstanding I/Os
expected on that particular reply queue.

Threaded ISR (secondary handler) will loop for I/O completion as long as
there are outstanding I/Os (speculative method using same per reply queue
outstanding counter) or it has completed some X amount of commands
(something like budget).

Link: https://lore.kernel.org/r/20210520152545.2710479-18-kashyap.desai@broadcom.com
Cc: sathya.prakash@broadcom.com
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Tomas Henzl <thenzl@redhat.com>
Reviewed-by: Himanshu Madhani <himanshu.madhani@oracle.com>
Signed-off-by: Kashyap Desai <kashyap.desai@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>