[media] rcar-fcp: Make sure rcar_fcp_enable() returns 0 on success

When resuming from suspend-to-RAM on r8a7795/salvator-x:

    dpm_run_callback(): pm_genpd_resume_noirq+0x0/0x90 returns 1
    PM: Device fe940000.fdp1 failed to resume noirq: error 1
    dpm_run_callback(): pm_genpd_resume_noirq+0x0/0x90 returns 1
    PM: Device fe944000.fdp1 failed to resume noirq: error 1
    dpm_run_callback(): pm_genpd_resume_noirq+0x0/0x90 returns 1
    PM: Device fe948000.fdp1 failed to resume noirq: error 1

According to its documentation, rcar_fcp_enable() returns 0 on success
or a negative error code if an error occurs.  Hence
fdp1_pm_runtime_resume() and vsp1_pm_runtime_resume() forward its return
value to their callers.

However, rcar_fcp_enable() forwards the return value of
pm_runtime_get_sync(), which can actually be 1 on success, leading to
the resume failure above.

To fix this, consider only negative values returned by
pm_runtime_get_sync() to be failures.

Fixes: 7b49235e ("[media] v4l: Add Renesas R-Car FCP driver")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/platform/rcar-fcp.c

@@ -99,10 +99,16 @@ EXPORT_SYMBOL_GPL(rcar_fcp_put);
  */
 int rcar_fcp_enable(struct rcar_fcp_device *fcp)
 {
+	int error;
+
 	if (!fcp)
 		return 0;
 
-	return pm_runtime_get_sync(fcp->dev);
+	error = pm_runtime_get_sync(fcp->dev);
+	if (error < 0)
+		return error;
+
+	return 0;
 }
 EXPORT_SYMBOL_GPL(rcar_fcp_enable);