Revert "drm/xe: flush gtt before signalling user fence on all engines"

This reverts commit 38007fa9.

Signaling user-fence after seqno write does not seem to be good solution.
Instead of changing order separate barrier should be put before user-fence,
this will be done in separate patch.

v2: added fixes tag in case reverted patch gets backported to stable

Fixes: 38007fa9

 ("drm/xe: flush gtt before signalling user fence on all engines")
Signed-off-by: Andrzej Hajda <andrzej.hajda@intel.com>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240605-fix_user_fence_posted-v3-1-06e7932f784a@intel.com