lantiq: VG3503J - use the same PHY led functionality as the OEM firmware

Based on the vg3503j_gphy_led.sh script published in the VG3503J wiki
article, the OEM Firmware uses the following PHY led functionality:

    gphy led 0: LINK/ACTIVITY
    gphy led 1: LINK
    gphy led 2: ACTIVITY

Signed-off-by: Mathias Kresin <openwrt@kresin.me>

SVN-Revision: 49278