drm/amdgpu: Fix interrupt handling in GFX v9.4.3

IH follows a different identification scheme for its clients. Get the
right mapping of xcc instance from IH node id.

Signed-off-by: Lijo Lazar <lijo.lazar@amd.com>
Reviewed-by: Le Ma <le.ma@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>