drm/xe: Assert that we manipulate the vm->rebind_list under the vm dma_resv

When evicting we might manipulate another vm's rebind list. Add an assert to make sure we catch these occurencies, which are intended to be fixed as part of #169 (closed).

Now the test ./xe_evict --r evict-cm-threads-small-multi-vm can be used as an igt for this as it hits this assert.

Signed-off-by: Thomas Hellström thomas.hellstrom@linux.intel.com