megaraid_sas: Make adprecovery variable atomic

Make instance->adprecovery variable atomic and removes hba_lock spinlock
while accessing instance->adprecovery.

Signed-off-by: Sumit Saxena <sumit.saxena@avagotech.com>
Signed-off-by: Kashyap Desai <kashyap.desai@avagotech.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>