sdhci: avoid changing voltage needlessly

Because of granularity issues, sometimes we told the hardware to change
to the voltage we were already at. Rework the logic so this doesn't
happen.

Signed-off-by: Pierre Ossman <pierre@ossman.eu>

drivers/mmc/host/sdhci.h

@@ -255,7 +255,7 @@ struct sdhci_host {
 	unsigned int		timeout_clk;	/* Timeout freq (KHz) */
 
 	unsigned int		clock;		/* Current clock (MHz) */
-	unsigned short		power;		/* Current voltage */
+	u8			pwr;		/* Current voltage */
 
 	struct mmc_request	*mrq;		/* Current request */
 	struct mmc_command	*cmd;		/* Current command */