Hwmod adaptation design requires each of the DSS HW IP to be a platform driver.
So a platform_driver for DISPC is created and init exit methods are moved from core.c
to its driver probe,remove. pdev member has to be maintained by its own drivers.

DISPC platform driver is registered from inside omap_dss_probe, in the order desired.
Signed-off-by: NSenthilvadivu Guruswamy <svadivu@ti.com>
Signed-off-by: NSumit Semwal <sumit.semwal@ti.com>
Signed-off-by: NTomi Valkeinen <tomi.valkeinen@ti.com>