ipq40xx: improve ASUS RT-AC58U support

ipq40xx: improve ASUS RT-AC58U support

This patch does the following:

- move WiFi LED setup to DTS
- fix LAN/WAN MAC addresses and add label MAC address
- wan5G -> wlan5G, power -> led_power
- increase flash SPI frequency to 30MHz

MAC addresses are stored in Factory partition at:
0x1006: WiFi 2.4GHz, WAN (label_mac)
0x5006: WiFi 5GHz, LAN (label_mac +4)

By improving flash speed,
`time dd if=/dev/mtdblock8 of=/dev/null bs=2k`
is reduced from 7m 10.26s to 5m 9.52s.
Using higher frequencies did not improve speed further.

Signed-off-by: Sungbo Eo <mans0n@gorani.run>