wifi: carl9170: do not ping device which has failed to load firmware

Syzkaller reports [1, 2] crashes caused by an attempts to ping
the device which has failed to load firmware. Since such a device
doesn't pass 'ieee80211_register_hw()', an internal workqueue
managed by 'ieee80211_queue_work()' is not yet created and an
attempt to queue work on it causes null-ptr-deref.

[1] https://syzkaller.appspot.com/bug?extid=9a4aec827829942045ff
[2] https://syzkaller.appspot.com/bug?extid=0d8afba53e8fb2633217



Fixes: e4a668c5 ("carl9170: fix spurious restart due to high latency")
Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru>
Acked-by: Christian Lamparter <chunkeey@gmail.com>
Link: https://patch.msgid.link/20250616181205.38883-1-dmantipov@yandex.ru


Signed-off-by: Jeff Johnson <jeff.johnson@oss.qualcomm.com>