scsi: esas2r: unlock on error in esas2r_nvram_read_direct()

This error path is missing an unlock.

Fixes: 26780d9e ("[SCSI] esas2r: ATTO Technology ExpressSAS 6G SAS/SATA RAID Adapter Driver")
Link: https://lore.kernel.org/r/20191022102324.GA27540@mwanda


Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>