drm/sun4i: dsi: Fix unitialized variable warning

Since the DPHY rework, one error path doesn't set the return error code
before jumping to its error label, which in turns make gcc (rightfully)
complain about the variable holding the error code being uninitialized.

Fix this.

Fixes: bb3b6fcb68 ("sun6i: dsi: Convert to generic phy handling")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190208090540.19626-1-maxime.ripard@bootlin.com

drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c

@@ -1025,6 +1025,7 @@ static int sun6i_dsi_probe(struct platform_device *pdev)
 	dsi->dphy = devm_phy_get(dev, "dphy");
 	if (IS_ERR(dsi->dphy)) {
 		dev_err(dev, "Couldn't get the MIPI D-PHY\n");
+		ret = PTR_ERR(dsi->dphy);
 		goto err_unprotect_clk;
 	}