drm/xe: Reword exec_queue and vm lock doc

Reword documentation to possibly what it meant to be.

Reviewed-by: Nirmoy Das <nirmoy.das@intel.com>
Reviewed-by: Jonathan Cavitt <jonathan.cavitt@intel.com>
Reviewed-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241104143815.2112272-4-lucas.demarchi@intel.com


Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>