scsi: megaraid_sas: Update LD map after populating drv_map driver map copy

Issue – There may be some IO accessing incorrect raid map, but driver
has checks in IO path to handle those cases. It is always better to move
to new raid map only once raid map is populated and validated.  No
functional defect. Fix is provided as part of review.  Fix – Update
instance->map_id after driver has populated new driver raid map from
firmware raid map.

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>