lantiq: set correct gphy pins for Zyxel P-2812

lantiq: set correct gphy pins for Zyxel P-2812

This fixes the gphy LED pins for Zyxel P-2812 devices. The have
been accidentally altered during a tidy-up operation (see Fixes:
below).

No ports were available, dmesg reported:

[ 0.658577] pinctrl-xway 1e100b10.pinmux: pin io5 already requested by
            1e100bb0.stp; cannot claim for 1e108000.eth
[ 0.667566] pinctrl-xway 1e100b10.pinmux: pin-5 (1e108000.eth) status -22
[ 0.685238] lantiq,xrx200-net 1e108000.eth: Error applying setting,
            reverse things back
[ 0.693270] lantiq,xrx200-net: probe of 1e108000.eth failed with error -22

Fixes: FS#3188
Fixes: 660200e53d62 ("lantiq: dts: assign the GPHY LED pins to the
Ethernet controller node")

Suggested-by: Mathias Kresin <dev@kresin.me>
Signed-off-by: Willem van den Akker <wvdakker@wilsoft.nl>
[commit message facelift]
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>