drm/i915: skylake primary plane scaling using shared scalers

This patch enables skylake primary plane scaling using shared
scalers atomic desgin.

v2:
-use single copy of scaler limits (Matt)

v3:
-move detach_scalers to crtc commit path (Matt)
-use values in plane_state->src as regular integers (me)

v4:
-changes to align with updated scaler structures (Matt, me)
-keep plane src rect in 16.16 format (Matt, Daniel)

v5:
-Rebased on top of 90/270 rotation changes (me)
-Fixed an issue introduced by 90/270 changes where plane programming
 is using drm_plane->state rect instead of intel_plane->state rect.
 This change also required for scaling to work properly. (me)
-With 90/270, updated limits to cover both portrait and landscape usages (me)
-Refactored skylake_update_primary_plane to reduce its size (Daniel)
 Added helper functions for refactoring are comprehended enough to be
 used for skylake_update_plane (for sprite) too. One stop towards
 having single function for all planes.

v6:
-Added fixme note when checking plane_state->src width in update_plane (Daniel)
-Release lock when failing to colorkey request with active scaler (Daniel)

Signed-off-by: Chandra Konduru <chandra.konduru@intel.com>
Reviewed-by:  <matthew.d.roper@intel.com>
Reviewed-by: sonika.jindal@intel.com (v5)
Testcase: igt/kms_plane_scaling
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>