drm/msm: use IS_ERR() to check regulator_get() return

regulator_get() never returns NULL. There's no need for IS_ERR_OR_NULL()
Signed-off-by: Fabian Frederick <fabf@skynet.be>
Signed-off-by: Rob Clark <robdclark@gmail.com>

drivers/gpu/drm/msm/dsi/dsi_host.c

@@ -273,7 +273,7 @@ static const struct dsi_config *dsi_get_config(struct msm_dsi_host *msm_host)
 	u32 major = 0, minor = 0;
 
 	gdsc_reg = regulator_get(&msm_host->pdev->dev, "gdsc");
-	if (IS_ERR_OR_NULL(gdsc_reg)) {
+	if (IS_ERR(gdsc_reg)) {
 		pr_err("%s: cannot get gdsc\n", __func__);
 		goto fail;
 	}