mmc: sdhci: using common mmc_regulator_set_vqmmc()

Switch to use the more robust common mmc_regulator_set_vqmmc()
function in MMC core which set the target voltage as close as
possible to target voltage.

We did not re-factor the whole sdhci_start_signal_voltage_switch()
cause we want to keep the original signal switch order between host
and card to avoid potential break.
Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/host/sdhci.c

@@ -1835,8 +1835,7 @@ static int sdhci_start_signal_voltage_switch(struct mmc_host *mmc,
 		sdhci_writew(host, ctrl, SDHCI_HOST_CONTROL2);
 
 		if (!IS_ERR(mmc->supply.vqmmc)) {
-			ret = regulator_set_voltage(mmc->supply.vqmmc, 2700000,
-						    3600000);
+			ret = mmc_regulator_set_vqmmc(mmc, ios);
 			if (ret) {
 				pr_warn("%s: Switching to 3.3V signalling voltage failed\n",
 					mmc_hostname(mmc));
@@ -1859,8 +1858,7 @@ static int sdhci_start_signal_voltage_switch(struct mmc_host *mmc,
 		if (!(host->flags & SDHCI_SIGNALING_180))
 			return -EINVAL;
 		if (!IS_ERR(mmc->supply.vqmmc)) {
-			ret = regulator_set_voltage(mmc->supply.vqmmc,
-					1700000, 1950000);
+			ret = mmc_regulator_set_vqmmc(mmc, ios);
 			if (ret) {
 				pr_warn("%s: Switching to 1.8V signalling voltage failed\n",
 					mmc_hostname(mmc));
@@ -1892,8 +1890,7 @@ static int sdhci_start_signal_voltage_switch(struct mmc_host *mmc,
 		if (!(host->flags & SDHCI_SIGNALING_120))
 			return -EINVAL;
 		if (!IS_ERR(mmc->supply.vqmmc)) {
-			ret = regulator_set_voltage(mmc->supply.vqmmc, 1100000,
-						    1300000);
+			ret = mmc_regulator_set_vqmmc(mmc, ios);
 			if (ret) {
 				pr_warn("%s: Switching to 1.2V signalling voltage failed\n",
 					mmc_hostname(mmc));