ramips: cleanup EX2700 and WN3000RPv3 LEDs

ramips: cleanup EX2700 and WN3000RPv3 LEDs

This patch cleans up the WN3000RPv3 and EX2700 setup, bringing it in line
with other similar devices:

The power led is a bicolor one. The bootloader brings the red side on at
powerup.

Instead of blinking the red side in diag.sh and need to forcefully turn it off
in 01_leds, this patch simplifies the setup by relying on the default off state
of the gpio-led driver for the red side and blinking the green side as with
other devices.

Signed-off-by: Thibaut VARENE <hacks@slashdirt.org>