sched_4bsd: update function name in comment

[mchoo]

Summary

In b43179fbe815 ("Create a new scheduler api..."), schedclock() was
renamed to sched_clock() but the function name in the comment remained
still. Update the comment to reflect up-to-date name for schedclock().

Fixes: b43179fbe815 ("Create a new scheduler api...")

[olce]

Mmm... Certainly, schedclock() should have been updated to sched_clock() in commit b43179fbe815 ("Create a new scheduler api..."), which renamed the function. But then, it is still technically true even today that sched_clock() actually updates the mentioned fields, it's just that it does so indirectly (through sched_clock_tick(), of which sched_clock() is the only caller). Keeping the mention of the upper-level function / entry point to the scheduler could be seen as clearer. The recently-introduced possibility to have multiple schedulers compiled in the same kernel lead to some ugly renames, and that's why sched_clock() was renamed to sched_4bsd_clock(). Conceptually, though, the interface function triggering the updates is still sched_clock() (it's how it is referenced from outside 4BSD). I'd slightly prefer having sched_clock() in the comment.

[mchoo]

Reflect @olce's suggestion