ath79: fix LEDs for D-Link DIR-842

The device has a total of 8 LEDs, 5 of which are controlled by the switch
(LAN 1-4, WAN). Only power, wifi and wps are controlled by the SoC.

 * led_power is on GPIO 5 (not 15), boot flashing sequence is now visible
 * remove led 'internet', since it is only connected to the switch
 * remove ucidef_set_led_switch for WAN from 01_leds, as it has no effect

Tested on revisions C1 and C3.

Signed-off-by: Sebastian Schaper <openwrt@sebastianschaper.net>
[adjust commit title]
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>