drm/amdkfd: Support dimgrey_cavefish KFD (v2)

Add KFD support for dimgrey cavefish.

v2: rebase (Alex)

Signed-off-by: Chengming Gui <Jack.Gui@amd.com>
Reviewed-by: Tao Zhou <tao.zhou1@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>