drm/amdgpu/vg20:support new UVD FW version naming convention

Vega20 UVD Firmware has a new version naming convention:
  [31, 30] for encode interface major
  [29, 24] for encode interface minor
  [15, 8] for decode interface minor
  [7, 0] for hardware family id

Signed-off-by: James Zhu <James.Zhu@amd.com>
Reviewed-by: Leo Liu <leo.liu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>