OMAPDSS: use platform_driver_probe for core/dispc/dss

The platform devices for omapdss, dss and dispc drivers are always
present, so we can use platform_driver_probe instead of
platform_driver_register.

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

diff --cc drivers/video/omap2/dss/core.c
Simple merge

diff --cc drivers/video/omap2/dss/dispc.c
Simple merge

diff --cc drivers/video/omap2/dss/dss.c
Simple merge