qtnfmac: switch to napi_gro_receive

Use napi_gro_receive() rather than netif_receive_skb() to improve
performance when GRO is enabled.

Signed-off-by: Sergey Matyukevich <sergey.matyukevich.os@quantenna.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>