ipmi: kcs_bmc: mark expected switch fall-through in kcs_bmc_handle_data

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

Addresses-Coverity-ID: 1465255 ("Missing break in switch")
Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>
Cc: Haiyue Wang <haiyue.wang@linux.intel.com>
Signed-off-by: Corey Minyard <cminyard@mvista.com>

drivers/char/ipmi/kcs_bmc.c

@@ -95,6 +95,7 @@ static void kcs_bmc_handle_data(struct kcs_bmc *kcs_bmc)
 	switch (kcs_bmc->phase) {
 	case KCS_PHASE_WRITE_START:
 		kcs_bmc->phase = KCS_PHASE_WRITE_DATA;
+		/* fall through */
 
 	case KCS_PHASE_WRITE_DATA:
 		if (kcs_bmc->data_in_idx < KCS_MSG_BUFSIZ) {