docs: scheduler: Fix outdated parameter of rebalance_domains

According to the function prototype of rebalance_domains(), its first
parameter is *rq* and the document need to be updated.
Signed-off-by: Tang Yizhou <tangyizhou@huawei.com>
Link: https://lore.kernel.org/r/20211221031818.23186-1-tangyizhou@huawei.comSigned-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/scheduler/sched-domains.rst

@@ -37,10 +37,10 @@ rebalancing event for the current runqueue has arrived. The actual load
 balancing workhorse, run_rebalance_domains()->rebalance_domains(), is then run
 in softirq context (SCHED_SOFTIRQ).
 
-The latter function takes two arguments: the current CPU and whether it was idle
-at the time the scheduler_tick() happened and iterates over all sched domains
-our CPU is on, starting from its base domain and going up the ->parent chain.
-While doing that, it checks to see if the current domain has exhausted its
+The latter function takes two arguments: the runqueue of current CPU and whether
+the CPU was idle at the time the scheduler_tick() happened and iterates over all
+sched domains our CPU is on, starting from its base domain and going up the ->parent
+chain. While doing that, it checks to see if the current domain has exhausted its
 rebalance interval. If so, it runs load_balance() on that domain. It then checks
 the parent sched_domain (if it exists), and the parent of the parent and so
 forth.