[SCSI] megaraid_sas: Performance boost fixes

Host lock is added back around queuecommand. Host lock removal can create race
conditon between ISR path(when RAID map update interrupt is raised) and IO
build path of driver, since IO build path is making use of RAID map, and in
case of RAID map update interrupt, old RAID map copy is memset to zero, which
some IOs may be referencing in build IO path.  Changes done for performance
boost- 1) Added code to set SMP IRQ affinity per CPU.  2) Pass MSI-x index,
while issuing sysPD IO.

Signed-off-by: Kashyap Desai <kashyap.desai@lsi.com>
Signed-off-by: Sumit Saxena <sumit.saxena@lsi.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>