scsi: megaraid_sas: Added support for shared host tagset for cpuhotplug

Fusion adapters can steer completions to individual queues, and
we now have support for shared host-wide tags.
So we can enable multiqueue support for fusion adapters.

Once driver enable shared host-wide tags, cpu hotplug feature is also
supported as it was enabled using below patchsets -
commit bf0beec0607d ("blk-mq: drain I/O when all CPUs in a hctx are
offline")

Currently driver has provision to disable host-wide tags using
"host_tagset_enable" module parameter.

Once we do not have any major performance regression using host-wide
tags, we will drop the hand-crafted interrupt affinity settings.

Performance is also meeting the expecatation - (used both none and
mq-deadline scheduler)
24 Drive SSD on Aero with/without this patch can get 3.1M IOPs
3 VDs consist of 8 SAS SSD on Aero with/without this patch can get 3.1M
IOPs.

Signed-off-by: Kashyap Desai <[email protected]>
Signed-off-by: Hannes Reinecke <[email protected]>
Signed-off-by: John Garry <[email protected]>
Tested-by: Douglas Gilbert <[email protected]>
Acked-by: Martin K. Petersen <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>

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