drm/xe/exec_queue: Rename xe_exec_queue::compute to xe_exec_queue::lr

The properties of this struct are used in long running context so
make that clear by renaming it to lr, in alignment with the rest
of the code.

Cc: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Francois Dugast <francois.dugast@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240613170348.723245-1-francois.dugast@intel.com
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>