drm/xe: Use run_ticks instead of runtime for client stats

Note that runtime is also used in the pm context, so it is confusing to
use the same name to denote run time of the drm client. Use a more
appropriate name for the client utilization.

While at it, drop the incorrect multi-lrc comment in the helper
description

v2: s/show_runtime/show_run_ticks/ (Rodrigo)

Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240524234744.1352543-1-umesh.nerlige.ramappa@intel.com