gpu: ipu-v3: Fix imx-ipuv3-crtc module autoloading

If of_node is set before calling platform_device_add, the driver core
will try to use of: modalias matching, which fails because the device
tree nodes don't have a compatible property set. This patch fixes
imx-ipuv3-crtc module autoloading by setting the of_node property only
after the platform modalias is set.

Fixes: 304e6be6 ("gpu: ipu-v3: Assign of_node of child platform devices to corresponding ports")
Reported-by: Dennis Gilmore <dennis@ausil.us>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Tested-By: Dennis Gilmore <dennis@ausil.us>
Cc: stable@vger.kernel.org # 4.4+
Signed-off-by: Dave Airlie <airlied@redhat.com>