drm/amdgpu: add spin lock to protect freed list in vm (v2)

there is a protection fault about freed list when OCL test.
add a spin lock to protect it.

v2: drop changes in vm_fini

Signed-off-by: JimQu <jim.qu@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
2 files changed