mmc: sdhci: fix "pwr may be used uninitialized" warning

This patch fixes a warning when compiling the sdhci driver:
  pwr may be used uninitialized in sdhci_set_power

Tested with the following compiler versions: 4.2.4 and 4.4.4
Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Reviewed-by: Wolfram Sang <w.sang@pengutronix.de>
Signed-off-by: Chris Ball <cjb@laptop.org>

drivers/mmc/host/sdhci.c

@@ -1050,11 +1050,9 @@ static void sdhci_set_clock(struct sdhci_host *host, unsigned int clock)
 
 static void sdhci_set_power(struct sdhci_host *host, unsigned short power)
 {
-	u8 pwr;
+	u8 pwr = 0;
 
-	if (power == (unsigned short)-1)
-		pwr = 0;
-	else {
+	if (power != (unsigned short)-1) {
 		switch (1 << power) {
 		case MMC_VDD_165_195:
 			pwr = SDHCI_POWER_180;