drm/amd/display: Add DCN302 support in amdgpu_dm (v2)

Handle CAVE_DIMGREY_CAVEFISH in amdgpu_dm

v2: fix rebase typo (Alex)

Signed-off-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>