drm/omap: fix YUV422 90/270 rotation with mirroring

When rotating 90/270 + mirroring with YUV422, the end result will have
adjacent pixels swapped. The problem is that
dispc_ovl_set_rotation_attrs() has wrong rotation values for these
cases.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>