omapfb: move vrfb into omapfb

VRFB is only used by omapfb, so we can move it under omapfb's directory.

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