reset: allow drivers to request probe deferral

If the requested reset controller is not yet available, have reset_control_get
and device_reset return -EPROBE_DEFER so the driver can decide to request
probe deferral.
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Acked-by: Shawn Guo <shawn.guo@linaro.org>
Reviewed-by: Stephen Warren <swarren@nvidia.com>

drivers/reset/core.c

@@ -167,7 +167,7 @@ struct reset_control *reset_control_get(struct device *dev, const char *id)
 
 	if (!rcdev) {
 		mutex_unlock(&reset_controller_list_mutex);
-		return ERR_PTR(-ENODEV);
+		return ERR_PTR(-EPROBE_DEFER);
 	}
 
 	rstc_id = rcdev->of_xlate(rcdev, &args);