ath79: further fixes for ZyXEL NBG6716

ath79: further fixes for ZyXEL NBG6716

This applies further fixes to the DTS of ZyXEL NBG6716 based on
what is found in ar71xx (mach-nbg6716.c):

- use WiFi label names as in ar71xx
- fix WPS gpio number
- fix GPIO_ACTIVE_HIGH and mode for WiFi switch
- add codes for USB eject buttons
- fix node name for "internet" LED

This device has separate LEDs for WAN and "Internet". As the WAN-LED
(and the four LAN-LEDs) are driven independent of the setup in
DT/01_leds, the "internet" LED is left unassigned (in contrast to
ar71xx, where it was set up effectively as a second WAN LED)

Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>