wifi: cfg80211: Add wiphy_delayed_work_pending()

Add wiphy_delayed_work_pending() to check if any delayed work timer is
pending, that can be used to be sure that wiphy_delayed_work_queue()
won't postpone an already pending delayed work.

Signed-off-by: Remi Pommarel <repk@triplefau.lt>
Link: https://patch.msgid.link/20240924192805.13859-2-repk@triplefau.lt


[fix return value kernel-doc]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>