[media] media: omap3isp: remove unused clkdev

No merged platform supplies xclks via platform data.  As we want to
slightly change the clkdev interface, rather than fixing this unused
code, remove it instead.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Sakari Ailus <sakari.ailus@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>