[media] omap3isp: Move the syscon register out of the ISP register maps

The syscon register isn't part of the ISP, use it through the syscom driver
regmap instead. The syscom block is considered to be from 343x on ISP
revision 2.0 whereas 15.0 is assumed to have 3630 syscon.

Signed-off-by: Sakari Ailus <sakari.ailus@iki.fi>
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>