wilc1000: Fix use of void pointer as a wrong struct type

ac_classify() expects a struct sk_buff* as its second argument, which is
a member of struct tx_complete_data. priv happens to be a pointer to
struct tx_complete_data, so passing it directly to ac_classify() leads
to wrong behaviour and occasional panics.

Since there is only one caller of wilc_wlan_txq_add_net_pkt and it
already knows the type behind this pointer, and the structure is already
in the header file, change the function signature to use the real type
instead of void* in order to prevent confusion.

Signed-off-by: Vsevolod Kozlov <zaba@mm.st>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/YCQomJ1mO5BLxYOT@Vsevolods-Mini.lan