OMAPDSS: Do not require a VDDS_DSI regulator on AM35xx

On our AM3505 based board, dpi.c complains that there is no VDDS_DSI
regulator and the framebuffer cannot be enabled. However, this check
does not seem to apply to AM3505/17 chips.

This patch adds new features list for AM35xxx, which is the same as for
OMAP3 except the VDDS_DSI is removed.

Signed-off-by: Raphael Assenat <raph@8d.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>