brcmfmac: use correct skb freeing helper when deleting flowring

Flowrings contain skbs waiting for transmission that were passed to us
by netif. It means we checked every one of them looking for 802.1x
Ethernet type. When deleting flowring we have to use freeing function
that will check for 802.1x type as well.

Freeing skbs without a proper check was leading to counter not being
properly decreased. This was triggering a WARNING every time
brcmf_netdev_wait_pend8021x was called.

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Acked-by: Arend van Spriel <arend@broadcom.com>
Cc: stable@vger.kernel.org # 4.5+
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>