drm/amdgpu: add osssys v6_0_0 ip headers v4

Add osssys v6_0_0 register offset and shift masks
header files (Hawking)

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