ramips: remove set_wifi_led function in 01_leds

ramips: remove set_wifi_led function in 01_leds

While we mostly use the ucidef_set_led_* functions directly in 01_leds
we still have the set_wifi_led function in parallel for several old
devices. This is not only inconsistent with the other definitions,
it also links to the wlan0 interface instead of using a phy trigger
which would be independent of the interface name (and is used for
all newer devices anyway). Apart from that, the standard names
"wifi" and "wifi-led" are not very helpful in a world with different
radio bands either.

Thus, this patch removes the set_wifi_led function and puts the
relevant commands into the cases explicitly. This makes the
mechanism used more evident and will hopefully lead to some future
improvements or at least prevent some copy-pasting of the old
setups.

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