drm/amd/display: Add KUnit test for CRC function

drm/amd/display: Add KUnit test for CRC function

DM CRC parsing functions are an easy candidate for exploring the use of
KUnit unit-testing frameworks. Add a few tests for the same.

The test file and .kunitconfig are placed under amdgpu_dm/tests/ to
follow the convention of keeping test code separate from production
sources.

Assisted-by: Copilot:Claude-Opus-4.6
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Ivan Lipski <ivan.lipski@amd.com>
Tested-by: Dan Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>