media: ov64a40: Do not match on endpoint

Before commit 1029939b ("media: v4l: async: Simplify async
sub-device fwnode matching") sensor drivers were encouraged on matching
on endpoints, to increase the accuracy of matching logic in v4l2-async.

After the framework changes in v6.6 in which endpoint matching has
been deprecated, sensor drivers are not supposed to initialized
sd->fwnode.

Drop it in ov64a40 driver and modify the error paths accordingly.

Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>