Move enable/disable_channel() from omap_dss_device to overlay manager.

This is part of a larger patch-set, which moves the control from omapdss
driver to the display driver.
Signed-off-by: NTomi Valkeinen <tomi.valkeinen@nokia.com>

Move wait_vsync() from omap_dss_device to overlay manager.

This is part of a larger patch-set, which moves the control from omapdss
driver to the display driver.
Signed-off-by: NTomi Valkeinen <tomi.valkeinen@nokia.com>

Add more core files to DSS2.
Signed-off-by: NTomi Valkeinen <tomi.valkeinen@nokia.com>