media: adv7604: Correct G/S_EDID behaviour

In order to have v4l2-compliance tool pass the G/S_EDID some modifications
where needed in the driver.
In particular, the edid.reserved zone must be blanked.

Signed-off-by: Jean-Michel Hautbois <jean-michel.hautbois@vodalys.com>
media: imx6 camera: G:S_EDID and format compliance