drm/msm/mdp5: Advertize 180 degree rotation

Since the hardware can apparently do both X and Y reflection, we
can advertize also 180 degree rotation as thats just X+Y reflection.

v2: Drop the BIT()

Cc: Rob Clark <robdclark@gmail.com>
Cc: Jilai Wang <jilaiw@codeaurora.org>
Cc: Archit Taneja <architt@codeaurora.org>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Rob Clark <robdclark@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1477077768-4274-3-git-send-email-ville.syrjala@linux.intel.com