omapfb/dss: change CONFIG_OMAP* to CONFIG_FB_OMAP*

We need to change the config symbols of omapfb's private copy of
omapdss so that we won't have config symbol conflicts.

This patch changes the symbols from omapdss using simple replacement of
CONFIG_OMAP* to CONFIG_FB_OMAP*.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Acked-by: Dave Airlie <airlied@gmail.com>
Acked-by: Rob Clark <robdclark@gmail.com>