mmc: meson-mx-sdio: mark expected switch fall-through

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

Notice that in this particular case, I replaced the "fall-through:"
comment with a proper "fall through", which is what GCC is
expecting to find.

Addresses-Coverity-ID: 1373880 ("Missing break in switch")
Signed-off-by: NGustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: NUlf Hansson <ulf.hansson@linaro.org>

drivers/mmc/host/meson-mx-sdio.c

@@ -294,7 +294,7 @@ static void meson_mx_mmc_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
 	switch (ios->power_mode) {
 	case MMC_POWER_OFF:
 		vdd = 0;
-		/* fall-through: */
+		/* fall through */
 	case MMC_POWER_UP:
 		if (!IS_ERR(mmc->supply.vmmc)) {
 			host->error = mmc_regulator_set_ocr(mmc,