drm/amdgpu: enumerate UMSCH HW IP

drm/amdgpu: enumerate UMSCH HW IP

This part enumerates a UMSCH block under hardware id (22) at version
2.2.0 rather than under VCN. Add the UMSCH hardware id, an IP enum
slot, and the discovery name/map entries so it is recognized. No IP
block is wired up yet; this only makes the IP discoverable.

The multimedia IP setup assumed VCN/VCE/UVD was always present; handle
the case where it is absent so init does not fail with -EINVAL.

Acked-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Boyuan Zhang <Boyuan.Zhang@amd.com>
Signed-off-by: Ruijing Dong <ruijing.dong@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>