OMAP2,3: DSS2: Use platform device to get baseaddr

DSS, DISPC, DSI, RFBI, VENC baseaddr can be obtained from platform_get_resource().
This API in turn picks the right silicon baseaddr from the hwmod database.
So hardcoding of base addr could be removed.

Reviewed-by: Paul Walmsley <paul@pwsan.com>
Reviewed-by: Kevin Hilman <khilman@ti.com>
Tested-by: Kevin Hilman <khilman@ti.com>
Signed-off-by: Sumit Semwal <sumit.semwal@ti.com>
Signed-off-by: Senthilvadivu Guruswamy <svadivu@ti.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>