cfg80211: delete redundant free code

When kzalloc failed and rdev->sacn_req or rdev->scan_msg is null, pass a
null pointer to kfree is redundant, delete it and return directly.

Signed-off-by: liuguoqiang <liuguoqiang@uniontech.com>
Link: https://lore.kernel.org/r/20211115092139.24407-1-liuguoqiang@uniontech.com


[remove now unused creq = NULL assigment]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>