drm/xe: Fix use after free when client stats are captured

drm/xe: Fix use after free when client stats are captured

xe_file_close triggers an asynchronous queue cleanup and then frees up
the xef object. Since queue cleanup flushes all pending jobs and the KMD
stores client usage stats into the xef object after jobs are flushed, we
see a use-after-free for the xef object. Resolve this by taking a
reference to xef from xe_exec_queue.

While at it, revert an earlier change that contained a partial work
around for this issue.

v2:
- Take a ref to xef even for the VM bind queue (Matt)
- Squash patches relevant to that fix and work around (Lucas)

v3: Fix typo (Lucas)

Fixes: ce62827bc294 ("drm/xe: Do not access xe file when updating exec queue run_ticks")
Fixes: 6109f24f87d7 ("drm/xe: Add helper to accumulate exec queue runtime")
Closes: https://gitlab.freedesktop.org/drm/xe/kernel/issues/1908
Signed-off-by: Umesh Nerlige Ramappa <[email protected]>
Reviewed-by: Matthew Brost <[email protected]>
Reviewed-by: Lucas De Marchi <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]
Signed-off-by: Lucas De Marchi <[email protected]>