drm/amdgpu: configure dimgrey_cavefish gfx according to gfx 10.3's definition

The gfx version of dimgrey_cavefish is 10.3, identical to sienna_cichlid, follow the way
of sienna_cichlid.

Signed-off-by: Tao Zhou <tao.zhou1@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Reviewed-by: Jiansong Chen <Jiansong.Chen@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>