drm/amdgpu: add vcn_v4_0 ip dump support

Add support of vcn ip dump in the devcoredump
for vcn_v4_0.

Signed-off-by: Sunil Khatri <sunil.khatri@amd.com>
Acked-by: Leo Liu <leo.liu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>