drm/amd/display: Enable ISHARP support for DCN401

drm/amd/display: Enable ISHARP support for DCN401

[Why]
Enable sharpener support for DCN401

[How]
- Removed memcmp check that was preventing ISHARP from being enabled.
- Add missing ISHARP register defines, masks, and writes.
- Add programming of Blur and Scale coefficients.
- Program FMT_MODE and NLDELTA registers based on LLS_PREF and pixel
- format
- Only enable ISHARP for YUV420
- Add disabling of ISHARP
- Add debug flags and registry keys for debugging ISHARP.
- Set default to medium level

Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Samson Tam <Samson.Tam@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>