ufs: fix NULL dereference when no regulators are defined

If no voltage supply regulators are defined for the UFS devices (assumed
they are always-on), ufshcd_config_vreg_load() can be called on
suspend/resume paths with vreg == NULL as hba->vreg_info.vcc* equal to
NULL, and it causes NULL pointer dereference.

This fixes it by making ufshcd_config_vreg_{h,l}pm noop when no regulators
are defined.

Signed-off-by: Akinobu Mita <mita@fixstars.com>
Reviewed-by: Subhash Jadavani <subhashj@codeaurora.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>

drivers/scsi/ufs/ufshcd.c

@@ -4268,12 +4268,18 @@ static int ufshcd_config_vreg_load(struct device *dev, struct ufs_vreg *vreg,
 static inline int ufshcd_config_vreg_lpm(struct ufs_hba *hba,
 					 struct ufs_vreg *vreg)
 {
+	if (!vreg)
+		return 0;
+
 	return ufshcd_config_vreg_load(hba->dev, vreg, UFS_VREG_LPM_LOAD_UA);
 }
 
 static inline int ufshcd_config_vreg_hpm(struct ufs_hba *hba,
 					 struct ufs_vreg *vreg)
 {
+	if (!vreg)
+		return 0;
+
 	return ufshcd_config_vreg_load(hba->dev, vreg, vreg->max_uA);
 }