drm/xe/bo: sync kernel fences for KMD buffers

With things like pipelined evictions, VRAM pages can be marked as free
and yet still have some active kernel fences, with the idea that the
next caller to allocate the memory will respect them. However it looks
like we are missing synchronisation for KMD internal buffers, like
page-tables, lrc etc. For userspace objects we should already have the
required synchronisation for CPU access via the fault handler, and
likewise for GPU access when vm_binding them.

To fix this synchronise against any kernel fences for all KMD objects at
creation. This should resolve some severe corruption seen during
evictions.

v2 (Matt B):
  - Revamp the comment explaining this. Also mention why USAGE_KERNEL is
    correct here.
v3 (Thomas):
  - Make sure to use ctx.interruptible for the wait.

Testcase: igt@xe-evict-ccs
Closes: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/853
Closes: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/855
Reported-by: Zbigniew Kempczyński <[email protected]>
Signed-off-by: Matthew Auld <[email protected]>
Cc: Thomas Hellström <[email protected]>
Cc: Matthew Brost <[email protected]>
Reviewed-by: Thomas Hellström <[email protected]>
Tested-by: Zbigniew Kempczyński <[email protected]>
Signed-off-by: Rodrigo Vivi <[email protected]>

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