drm/i915/skl: Support for 90/270 rotation

drm/i915/skl: Support for 90/270 rotation

v2: Moving creation of property in a function, checking for 90/270
rotation simultaneously (Chris)
Letting primary plane to be positioned
v3: Adding if/else for 90/270 and rest params programming, adding check for
pixel_format, some cleanup (review comments)
v4: Adding right pixel_formats, using src_* params instead of crtc_* for offset
and size programming (Ville)
v5: Rebased on -nightly and Tvrtko's series for gtt remapping.
v6: Rebased on -nightly (Tvrtko's series merged)
v7: Moving pixel_format check to intel_atomic_plane_check (Matt)

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