scsi: megaraid_sas: Avoid firing DCMDs while OCR is in progress

Driver needs to avoid PCI writes while OCR is in progress.  Use
reset_mutex to synchronize between firing DCMDs MR_DCMD_PD_GET_INFO and
MR_DCMD_DRV_GET_TARGET_PROP while OCR is triggered.  Without this fix,
if Device/VD add/creation is in progress and at the same time MR
Firmware is going through OCR, user may see OCR never completed and it
may need system reboot.  This scenario is rare to occur. Fix is provided
as part of review.

Signed-off-by: Sumit Saxena <sumit.saxena@broadcom.com>
Signed-off-by: Shivasharan S <shivasharan.srikanteshwara@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>