drm/msm/dsi: invalid parameter check in msm_dsi_phy_enable

The function performs a check on the "phy" input parameter, however, it
is used before the check.

Initialize the "dev" variable after the sanity check to avoid a possible
NULL pointer dereference.

Fixes: 5c829028 ("drm/msm/dsi: Split PHY drivers to separate files")
Addresses-Coverity-ID: 1493860 ("Null pointer dereference")
Signed-off-by: José Expósito <jose.exposito89@gmail.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://lore.kernel.org/r/20220116181844.7400-1-jose.exposito89@gmail.comSigned-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

drivers/gpu/drm/msm/dsi/phy/dsi_phy.c

@@ -808,12 +808,14 @@ int msm_dsi_phy_enable(struct msm_dsi_phy *phy,
 			struct msm_dsi_phy_clk_request *clk_req,
 			struct msm_dsi_phy_shared_timings *shared_timings)
 {
-	struct device *dev = &phy->pdev->dev;
+	struct device *dev;
 	int ret;
 
 	if (!phy || !phy->cfg->ops.enable)
 		return -EINVAL;
 
+	dev = &phy->pdev->dev;
+
 	ret = dsi_phy_enable_resource(phy);
 	if (ret) {
 		DRM_DEV_ERROR(dev, "%s: resource enable failed, %d\n",