drm/amdgpu: Create version number for coredumps

Even if there's nothing currently parsing amdgpu's coredump files, if
we eventually have such tools they will be glad to find a version field
to properly read the file.

Create a version number to be displayed on top of coredump file, to be
incremented when the file format or content get changed.

Signed-off-by: André Almeida <andrealmeid@igalia.com>
Reviewed-by: Shashank Sharma <shashank.sharma@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>