drm: Check crtc viewport correctly with rotated primary plane on atomic drivers

On atomic drivers we can dig out the primary plane rotation from the
plane state instead of looking at the legacy crtc->invert_dimensions
flag. The flag is not set by anyone except omapdrm, and it would be
racy to set it the same way in the atomic helpers.

v2: Kill crtc->invert_dimensions totally since omap is state based
    already and no one else ever used it (Matt)

Cc: Matt Roper <matthew.d.roper@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
Cc: Rob Clark <robdclark@gmail.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1445009919-22746-1-git-send-email-ville.syrjala@linux.intel.com


Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>