qtnfmac: switch to netif_napi_add_weight()

qtnfmac chooses its own magic NAPI weight so switch to the new
API created for those who don't use NAPI_POLL_WEIGHT.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20220504163316.549648-4-kuba@kernel.org