mmc: Rename timeout parameters for clarification

It's quite hard to figure out time units for various function that have
timeout parameters. This leads to possible errors when one forgets to
convert ms to us, for example. Let's rename those parameters
correspondingly to 'timeout_us' and 'timeout_ms' to prevent such issues
further.

While at it, add time units info as comments to struct mmc fields.

This commit doesn't change the behavior, only renames parameters names.
Buildman should report no changes at all.

Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
Reviewed-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Igor Opaniuk <igor.opaniuk@gmail.com>
diff --git a/drivers/mmc/renesas-sdhi.c b/drivers/mmc/renesas-sdhi.c
index 7c53aa2..0cb65b4 100644
--- a/drivers/mmc/renesas-sdhi.c
+++ b/drivers/mmc/renesas-sdhi.c
@@ -499,15 +499,16 @@
 }
 
 #if CONFIG_IS_ENABLED(MMC_UHS_SUPPORT)
-static int renesas_sdhi_wait_dat0(struct udevice *dev, int state, int timeout)
+static int renesas_sdhi_wait_dat0(struct udevice *dev, int state,
+				  int timeout_us)
 {
 	int ret = -ETIMEDOUT;
 	bool dat0_high;
 	bool target_dat0_high = !!state;
 	struct tmio_sd_priv *priv = dev_get_priv(dev);
 
-	timeout = DIV_ROUND_UP(timeout, 10); /* check every 10 us. */
-	while (timeout--) {
+	timeout_us = DIV_ROUND_UP(timeout_us, 10); /* check every 10 us. */
+	while (timeout_us--) {
 		dat0_high = !!(tmio_sd_readl(priv, TMIO_SD_INFO2) & TMIO_SD_INFO2_DAT0);
 		if (dat0_high == target_dat0_high) {
 			ret = 0;