Revert "bcmdhd: disable GAN_LITE_NAT_KEEPALIVE_FILTER"

This reverts commit 75d32dc8e3136e0c171503126b2737f46f69e5cb.
Revert "Revert "bcmdhd: disable GAN_LITE_NAT_KEEPALIVE_FILTER""

This reverts commit 357944f42eb7b70c438b4e1f023cec91c4c2246d.