scsi: mpi3mr: Unlock on error path

There is some clean up necessary before returning.  Smatch complains:

    drivers/scsi/mpi3mr/mpi3mr_fw.c:4786 mpi3mr_soft_reset_handler()
    warn: inconsistent returns '&mrioc->reset_mutex'.
      Locked on  : 4730
      Unlocked on: 4786

Link: https://lore.kernel.org/r/YtVCEsxMU8buuMjP@kili
Fixes: f10af057

 ("scsi: mpi3mr: Resource Based Metering")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>