ARM: dts: BCM5301X: Add missing Netgear R8000 LEDs and Keys

Added two WAN status LEDs and a GPIO key for brightness which were
missing.

Signed-off-by: Aditya Xavier <adityaxavier@gmail.com>
Acked-by: Rafał Miłecki <rafal@milecki.pl>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>