drm/amdgpu: add ih v6_0 ip block v2

This adds ih v6_0 ip block support.  IH is the
interrupt handler.

Signed-off-by: Stanley.Yang <Stanley.Yang@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>