drm: Add support for optional per-plane rotation property

drm: Add support for optional per-plane rotation property

Not all planes on the system may support the same rotations/reflections,
so make it possible to create a separate property for each plane.
This way userspace gets told exactly which rotations/reflections are
possible for each plane.

v2: Add drm_plane_create_rotation_property() helper
v3: Drop the BIT(), __builtin_ffs(x) - 1,
    Moar WARNs for bad parameters
    Deal with superfluous code shuffling

Signed-off-by: Ville Syrjälä <[email protected]>
Reviewed-by: Chris Wilson <[email protected]> (v1)
Reviewed-by: Joonas Lahtinen <[email protected]>
Signed-off-by: Daniel Vetter <[email protected]>
Link: http://patchwork.freedesktop.org/patch/msgid/[email protected]