drm/i915/display: Add Nearest-neighbor based integer scaling support

drm/i915/display: Add Nearest-neighbor based integer scaling support

Integer scaling (IS) is a nearest-neighbor upscaling technique that
simply scales up the existing pixels by an integer
(i.e., whole number) multiplier.Nearest-neighbor (NN) interpolation
works by filling in the missing color values in the upscaled image
with that of the coordinate-mapped nearest source pixel value.

Both IS and NN preserve the clarity of the original image. Integer
scaling is particularly useful for pixel art games that rely on
sharp, blocky images to deliver their distinctive look.

Introduce functions to configure the scaler filter coefficients to
enable nearest-neighbor filtering.

Bspec: 49247

changes since v6:
* Trust compiler, remove pointless inline keyword from cnl_coef_tap()
  & cnl_nearest_filter_coef() functions (Ville)
changes since v4:
* Make cnl_coef_tap(), cnl_nearest_filter_coef() inline (Uma)
changes since v3:
* None
changes since v2:
* Move APIs from 5/5 into this patch.
* Change filter programming related function names to cnl_*, move
  filter select bits related code into inline function (Ville)
changes since v1:
* Rearrange skl_scaler_setup_nearest_neighbor_filter() to iterate the
  registers directly instead of the phases and taps (Ville)

changes since RFC:
* Refine the skl_scaler_setup_nearest_neighbor_filter() logic (Ville)

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Uma Shankar <uma.shankar@intel.com>
Signed-off-by: Shashank Sharma <shashank.sharma@intel.com>
Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Signed-off-by: Pankaj Bharadiya <pankaj.laxminarayan.bharadiya@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201020161427.6941-4-pankaj.laxminarayan.bharadiya@intel.com