wifi: mt76: add wcid publish check in mt76_sta_add

In the Linux kernel, the following vulnerability has been resolved:

wifi: mt76: add wcid publish check in mt76_sta_add

Since mt7925_mac_sta_add publishes wcid, add publish check in mt76_sta_add
to avoid reinitializing the wcid->poll_list.

Found dev->sta_poll_list corruption when using mt7925 and 7.1-rc4.
According to the corruption information, prev->next was changed to itself.

wlan0: disconnect from AP 90:fb:5d:94:8b:e3 for new auth to 90:fb:5d:94:8b:e2
wlan0: authenticate with 90:fb:5d:94:8b:e2 (local address=84:9e:56:9c:7e:6b)
wlan0: send auth to 90:fb:5d:94:8b:e2 (try 1/3)
slab kmalloc-8k start ffff8c80958a6000 pointer offset 4160 size 8192
list_add corruption. prev->next should be next (ffff8c808a7488f8), but was ffff8c80958a7040. (prev=ffff8c80958a7040).

mt76_wcid_add_poll+0x95/0xd0 [mt76]
mt7925_mac_add_txs.part.0+0xa5/0xe0 [mt7925_common]
mt7925_rx_check+0xa7/0xc0 [mt7925_common]
mt76_dma_rx_poll+0x50d/0x790 [mt76]
mt792x_poll_rx+0x52/0xe0 [mt792x_lib]