media: staging: drop omap4iss

The omap4 camera driver has seen no progress since forever, and
now OMAP4 support has also been dropped from u-boot (1). So it is
time to retire this driver.

(1): https://lists.denx.de/pipermail/u-boot/2024-July/558846.html



Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>