wifi: rtlwifi: wait for firmware loading before releasing memory

At probe error path, the firmware loading work may have already been
queued. In such a case, it will try to access memory allocated by the probe
function, which is about to be released. In such paths, wait for the
firmware worker to finish before releasing memory.

Fixes: a7f7c15e ("rtlwifi: rtl8192cu: Free ieee80211_hw if probing fails")
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@igalia.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://patch.msgid.link/20241107133322.855112-4-cascardo@igalia.com