UPSTREAM: mac80211: mlme: find auth challenge directly

There's no need to parse all elements etc. just to find the
authentication challenge - use cfg80211_find_elem() instead.
This also allows us to remove WLAN_EID_CHALLENGE handling
from the element parsing entirely.

Bug: 254180332
Bug: 256770696
Link: https://lore.kernel.org/r/20210920154009.45f9b3a15722.Ice3159ffad03a007d6154cbf1fb3a8c48489e86f@changeid


Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Lee Jones <joneslee@google.com>
(cherry picked from commit 66dacdbc)
Change-Id: Ife49cbad96bb43064449d93b8f8ada9db24be540
(cherry picked from commit 12bd079b)