once: don't use a work queue to reset sleepable static key

Pointless overhead to use a work queue to reset the static key for a
DO_ONCE_SLEEPABLE() invocation.

Note that the previous code path included a BUG_ON() if the static key
was already disabled. Dropped that as part of this change because:
1) Use of BUG_ON() is highly discouraged.
2) There is a WARN_ON() in the static_branch_disable() code path
   that would provide adequate breadcrumbs to debug any issue.

Link: https://lkml.kernel.org/r/aWU4tfTju1l3oZCu@agluck-desk3
Signed-off-by: Tony Luck <[email protected]>
Reported-by: Reinette Chatre <[email protected]>
Cc: Eric Dumazet <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

lib/once.c

@@ -93,6 +93,6 @@ void __do_once_sleepable_done(bool *done, struct static_key_true *once_key,
 {
 	*done = true;
 	mutex_unlock(&once_mutex);
-	once_disable_jump(once_key, mod);
+	static_branch_disable(once_key);
 }
 EXPORT_SYMBOL(__do_once_sleepable_done);