ARM: OMAP: Disable venc for OMAP4

This is a alternative to "HACK: OMAP: DSS2: VENC: disable VENC on OMAP4 to
prevent crash" (ba02fa37de) by Tomi Valkeinen <tomi.valkeinen@ti.com> to prevent
VENC from crashing OMAP4 kernel. This prevents OMAPDSS from initial registration
of a device for VENC on OMAP4.

Signed-off-by: Chandrabhanu Mahapatra <cmahapatra@ti.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>