OMAPDSS: DPI: Remove cpu_is_xxxx checks

The OMAP3 checks have been removed and replaced by a dss feature
FEAT_DPI_USES_VDDS_DSI for cleaner implementation. The patches
"OMAP: DSS2: enable VDDS_DSI when using DPI" (8a2cfea8cc) by Tomi Valkeinen
<tomi.valkeinen@nokia.com> and "ARM: omap: fix oops in
drivers/video/omap2/dss/dpi.c" (4041071571) by Russell King
<rmk+kernel@arm.linux.org.uk> had introduced these checks. As it is evident
from these patches a dependency exists for some DSS pins on VDDS_DSI which is
better shown by dss feature FEAT_DPI_USES_VDDS_DSI.

Signed-off-by: Chandrabhanu Mahapatra <cmahapatra@ti.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
diff --git a/drivers/video/omap2/dss/dss_features.c b/drivers/video/omap2/dss/dss_features.c
index 9387097..2fe39d6 100644
--- a/drivers/video/omap2/dss/dss_features.c
+++ b/drivers/video/omap2/dss/dss_features.c
@@ -373,6 +373,7 @@
 	FEAT_ALPHA_FIXED_ZORDER,
 	FEAT_FIFO_MERGE,
 	FEAT_OMAP3_DSI_FIFO_BUG,
+	FEAT_DPI_USES_VDDS_DSI,
 };
 
 static const enum dss_feat_id omap3630_dss_feat_list[] = {