scsi: mpi3mr: Fix warnings reported by smatch

Fix the following warning reported by static analysis tool smatch:

smatch warnings:
drivers/scsi/mpi3mr/mpi3mr_os.c:873 mpi3mr_update_tgtdev() error: we
previously assumed 'mrioc->shost' could be null (see line 870

Link: https://lore.kernel.org/r/20210629141153.3158-1-sreekanth.reddy@broadcom.com
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Sreekanth Reddy <sreekanth.reddy@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/mpi3mr/mpi3mr_os.c

@@ -867,8 +867,9 @@ static void mpi3mr_update_tgtdev(struct mpi3mr_ioc *mrioc,
 		if ((dev_info & MPI3_DEVICE0_PCIE_DEVICE_INFO_TYPE_MASK) !=
 		    MPI3_DEVICE0_PCIE_DEVICE_INFO_TYPE_NVME_DEVICE)
 			tgtdev->is_hidden = 1;
-		if (mrioc->shost)
-			prot_mask = scsi_host_get_prot(mrioc->shost);
+		if (!mrioc->shost)
+			break;
+		prot_mask = scsi_host_get_prot(mrioc->shost);
 		if (prot_mask & SHOST_DIX_TYPE0_PROTECTION) {
 			scsi_host_set_prot(mrioc->shost, prot_mask & 0x77);
 			ioc_info(mrioc,