mmc: sdhci: Add regulator support for vccq (voltage regualor)

On some systems the host controller does not support vccq
signaling.  This is supplied by a dedicated regulator (vqmmc).
Add support for this regulator.

Signed-off-by: Philip Rakity <prakity@marvell.com>
Signed-off-by: Chris Ball <cjb@laptop.org>
diff --git a/include/linux/mmc/sdhci.h b/include/linux/mmc/sdhci.h
index ac83b10..fa8529a 100644
--- a/include/linux/mmc/sdhci.h
+++ b/include/linux/mmc/sdhci.h
@@ -97,7 +97,8 @@
 
 	const struct sdhci_ops *ops;	/* Low level hw interface */
 
-	struct regulator *vmmc;	/* Power regulator */
+	struct regulator *vmmc;		/* Power regulator (vmmc) */
+	struct regulator *vqmmc;	/* Signaling regulator (vccq) */
 
 	/* Internal data */
 	struct mmc_host *mmc;	/* MMC structure */