scsi: ufs: Allow regulators being always-on

Introduce a flag "always_on" in struct ufs_vreg to allow vendors to keep
the regulator always-on.

Link: https://lore.kernel.org/r/20201207054955.24366-2-stanley.chu@mediatek.comReviewed-by: NAndy Teng <andy.teng@mediatek.com>
Signed-off-by: NStanley Chu <stanley.chu@mediatek.com>
Signed-off-by: NMartin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/ufs/ufs.h

@@ -512,6 +512,7 @@ struct ufs_query_res {
 struct ufs_vreg {
 	struct regulator *reg;
 	const char *name;
+	bool always_on;
 	bool enabled;
 	int min_uV;
 	int max_uV;

drivers/scsi/ufs/ufshcd.c

@@ -8012,7 +8012,7 @@ static int ufshcd_disable_vreg(struct device *dev, struct ufs_vreg *vreg)
 {
 	int ret = 0;
 
-	if (!vreg || !vreg->enabled)
+	if (!vreg || !vreg->enabled || vreg->always_on)
 		goto out;
 
 	ret = regulator_disable(vreg->reg);