scsi: mptscsih: Mark expected switch fall-throughs

In preparation to enabling -Wimplicit-fallthrough, mark switch cases
where we are expecting to fall through.

This patch fixes the following warnings:

drivers/message/fusion/mptscsih.c: In function  mptscsih_io_done :
drivers/message/fusion/mptscsih.c:741:7: warning: this statement may fall through [-Wimplicit-fallthrough=]
    if ( ioc->bus_type == SAS ) {
       ^
drivers/message/fusion/mptscsih.c:790:3: note: here
   case MPI_IOCSTATUS_SCSI_TASK_TERMINATED: /* 0x0048 */
   ^~~~
drivers/message/fusion/mptscsih.c:884:4: warning: this statement may fall through [-Wimplicit-fallthrough=]
    scsi_set_resid(sc, 0);
    ^~~~~~~~~~~~~~~~~~~~~
drivers/message/fusion/mptscsih.c:885:3: note: here
   case MPI_IOCSTATUS_SCSI_RECOVERED_ERROR: /* 0x0040 */
   ^~~~

Warning level 3 was used: -Wimplicit-fallthrough=3

This patch is part of the ongoing efforts to enable
-Wimplicit-fallthrough.
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/message/fusion/mptscsih.c

@@ -786,6 +786,7 @@ mptscsih_io_done(MPT_ADAPTER *ioc, MPT_FRAME_HDR *mf, MPT_FRAME_HDR *mr)
 			/*
 			 * Allow non-SAS & non-NEXUS_LOSS to drop into below code
 			 */
+			/* Fall through */
 
 		case MPI_IOCSTATUS_SCSI_TASK_TERMINATED:	/* 0x0048 */
 			/* Linux handles an unsolicited DID_RESET better
@@ -882,6 +883,7 @@ mptscsih_io_done(MPT_ADAPTER *ioc, MPT_FRAME_HDR *mf, MPT_FRAME_HDR *mr)
 
 		case MPI_IOCSTATUS_SCSI_DATA_OVERRUN:		/* 0x0044 */
 			scsi_set_resid(sc, 0);
+			/* Fall through */
 		case MPI_IOCSTATUS_SCSI_RECOVERED_ERROR:	/* 0x0040 */
 		case MPI_IOCSTATUS_SUCCESS:			/* 0x0000 */
 			sc->result = (DID_OK << 16) | scsi_status;