wifi: mac80211: fix invalid drv_sta_pre_rcu_remove calls for non-uploaded sta

Avoid potential data corruption issues caused by uninitialized driver
private data structures.

Reported-by: Brian Coverstone <brian@mainsequence.net>
Fixes: 6a9d1b91 ("mac80211: add pre-RCU-sync sta removal driver operation")
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Link: https://lore.kernel.org/r/20230324120924.38412-3-nbd@nbd.name


Signed-off-by: Johannes Berg <johannes.berg@intel.com>