mmc: core: Clarify usage of mmc_set_signal_voltage()

The mmc_set_signal_voltage() function is used for SD/SDIO when switching to
1.8V for UHS mode. To clarify this let's do the following changes.

- We are always providing MMC_SIGNAL_VOLTAGE_180 as the signal_voltage
parameter to the function. Then, let's just remove the parameter as it
serves no purpose.
- Rename the function to mmc_set_uhs_voltage().

Signed-off-by: Ulf Hansson <[e-mail]>
Reviewed-by: Shawn Lin <[e-mail]>
Tested-by: Jan Glauber <[e-mail]>
Tested-by: Stefan Wahren <[e-mail]>

drivers/mmc/core/core.c

···
 
 }
 
-int mmc_set_signal_voltage(struct mmc_host *host, int signal_voltage, u32 ocr)
+int mmc_set_uhs_voltage(struct mmc_host *host, u32 ocr)
 {
 	struct mmc_command cmd = {};
 	int err = 0;
···
 	host->ios.clock = 0;
 	mmc_set_ios(host);
 
-	if (__mmc_set_signal_voltage(host, signal_voltage)) {
+	if (__mmc_set_signal_voltage(host, MMC_SIGNAL_VOLTAGE_180)) {
 		/*
 		 * Voltages may not have been switched, but we've already
 		 * sent CMD11, so a power cycle is required anyway

drivers/mmc/core/core.h

···
 void mmc_set_bus_mode(struct mmc_host *host, unsigned int mode);
 void mmc_set_bus_width(struct mmc_host *host, unsigned int width);
 u32 mmc_select_voltage(struct mmc_host *host, u32 ocr);
-int mmc_set_signal_voltage(struct mmc_host *host, int signal_voltage, u32 ocr);
+int mmc_set_uhs_voltage(struct mmc_host *host, u32 ocr);
 int __mmc_set_signal_voltage(struct mmc_host *host, int signal_voltage);
 void mmc_set_timing(struct mmc_host *host, unsigned int timing);
 void mmc_set_driver_type(struct mmc_host *host, unsigned int drv_type);

drivers/mmc/core/sd.c

···
 	 */
 	if (!mmc_host_is_spi(host) && rocr &&
 	   ((*rocr & 0x41000000) == 0x41000000)) {
-		err = mmc_set_signal_voltage(host, MMC_SIGNAL_VOLTAGE_180,
-					pocr);
+		err = mmc_set_uhs_voltage(host, pocr);
 		if (err == -EAGAIN) {
 			retries--;
 			goto try_again;

drivers/mmc/core/sdio.c

···
 	 * to make sure which speed mode should work.
 	 */
 	if (!powered_resume && (rocr & ocr & R4_18V_PRESENT)) {
-		err = mmc_set_signal_voltage(host, MMC_SIGNAL_VOLTAGE_180,
-					ocr_card);
+		err = mmc_set_uhs_voltage(host, ocr_card);
 		if (err == -EAGAIN) {
 			mmc_sdio_resend_if_cond(host, card);
 			retries--;