media: dt-bindings: media: ov772x: Make bus-type mandatory
In order to establish required properties based on the selected
bus type, make the 'bus-type' property mandatory. As this change
documents an endpoint property, also document the 'remote-endpoint'
one now that the 'endpoint' schema has been expanded.
Binary compatibility with existing DTB is kept as the driver does not
enforce the property to be present, and shall fall-back to default
parallel bus configuration, which was the only supported bus type, if
the property is not specified.