OMAP2, 3: DSS2: VENC: create platform_driver, move init, exit to driver

Hwmod adaptation design requires each of the DSS HW IP to be a platform driver.
So a platform_driver for VENC 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.

Also, venc_vdda_dac reading is moved to venc.c.

VENC platform driver is registered from inside omap_dss_probe, in the order desired.

Signed-off-by: Senthilvadivu Guruswamy <svadivu@ti.com>
Signed-off-by: Sumit Semwal <sumit.semwal@ti.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>

arch/arm/mach-omap2/board-omap3beagle.c

@@ -232,7 +232,7 @@ static struct omap_dss_board_info beagle_dss_data = {
 };
 
 static struct regulator_consumer_supply beagle_vdac_supply =
-	REGULATOR_SUPPLY("vdda_dac", "omapdss");
+	REGULATOR_SUPPLY("vdda_dac", "omapdss_venc");
 
 static struct regulator_consumer_supply beagle_vdvi_supply =
 	REGULATOR_SUPPLY("vdds_dsi", "omapdss");