docs: scheduler: Fix outdated parameter of rebalance_domains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 <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jonathan Corbet <[e-mail]>

Documentation/scheduler/sched-domains.rst

···
 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.