drm/xe: Remove TEST_VM_ASYNC_OPS_ERROR

TEST_VM_ASYNC_OPS_ERROR is broken and unused. Remove for now and will
pull back in a later time when it is used, fixed, and properly hidden
behind a Kconfig option. Also fixup the supported flags value.

Fixes: dd08ebf6 ("drm/xe: Introduce a new DRM driver for Intel GPUs")
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240206045010.2981051-1-matthew.brost@intel.com