wifi: rtl8xxxu: Fix skb misuse in TX queue selection

rtl8xxxu_queue_select() selects the wrong TX queues because it's
reading memory from the wrong address. It expects to find ieee80211_hdr
at skb->data, but that's not the case after skb_push(). Move the call
to rtl8xxxu_queue_select() before the call to skb_push().

Fixes: 26f1fad2 ("New driver: rtl8xxxu (mac80211)")
Signed-off-by: Bitterblue Smith <rtl8821cerfe2@gmail.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/7fa4819a-4f20-b2af-b7a6-8ee01ac49295@gmail.com