wil6210: fix call to wil6210_disconnect during unload

Move the call to wil6210_disconnect so it will be called
before unregister_netdevice. This is because it calls
netif_carrier_off which is forbidden to call on an
unregistered net device. Calling netif_carrier_off can
add a link watch event which might be handled after
net device was freed, causing a kernel oops.

Signed-off-by: Lior David <liord@codeaurora.org>
Signed-off-by: Maya Erez <merez@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>