drm/amdgpu: remove deprecated MES version vars

MES scheduler and kiq versions are stored in mes.sched_version and
mes.kiq_version, respectively, which are read from a register after
their queues are initialized. Remove mes.ucode_fw_version and
mes.data_fw_version which tried to read this versioning info from the
firmware headers (which don't contain this information).

Signed-off-by: Graham Sider <Graham.Sider@amd.com>
Reviewed-by: Jack Xiao <Jack.Xiao@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>