drm/amdgpu: Expose TA FW version in fw_version file

Reporting the fw_version just returns 0, the actual version is kept as
ta_*_ucode_version. This is the same as the feature reported in
the amdgpu_firmware_info debugfs file.

Signed-off-by: Kent Russell <kent.russell@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>