mmc: mmci: Clear busy_status when starting command

If we are starting a command which can generate a busy
response, then clear the variable host->busy_status
if the variant is using a ->busy_complete callback.

We are lucky that the member is zero by default and
hopefully always gets cleared in the ->busy_complete
callback even on errors, but it's just fragile so
make sure it is always initialized to zero.
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20230405-pl180-busydetect-fix-v7-1-69a7164f2a61@linaro.orgSigned-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/host/mmci.c

@@ -1238,6 +1238,7 @@ mmci_start_command(struct mmci_host *host, struct mmc_command *cmd, u32 c)
 			c |= host->variant->cmdreg_srsp;
 	}
 
+	host->busy_status = 0;
 	if (host->variant->busy_timeout && cmd->flags & MMC_RSP_BUSY) {
 		if (!cmd->busy_timeout)
 			cmd->busy_timeout = 10 * MSEC_PER_SEC;