media: nuvoton: Fix an error check in npcm_video_ece_init()

In the Linux kernel, the following vulnerability has been resolved:

media: nuvoton: Fix an error check in npcm_video_ece_init()

When function of_find_device_by_node() fails, it returns NULL instead of

an error code. So the corresponding error check logic should be modified

to check whether the return value is NULL and set the error code to be

returned as -ENODEV.