mediatek: improve device tree for Acer Predator Connect W6

mediatek: improve device tree for Acer Predator Connect W6

In order to prepare for OpenWrt support other Acer W6 devices and to get
a step further to full hardware support for Acer Predator Connect W6, this
commit
- adjusts the product name ("Acer Predator Connect W6")
- updates gpio LED labels to function/color scheme
- show router status by using first rgb led instead of it's red color only
  (blue: booting/failsafe mode; red: sysupgrade; green: running – was: red)
- changes switch/eth1 led configuration to reflect RX/TX activity and speed
  (green: full 1Gbps/2.5Gbps speed; amber: lower speed; blink: RX/TX)
- shortens dummy dm-mod.create string in bootargs
- enables W6's i2c interface

This is the third of four commits into which the original commit was split
to make reviews easier and more targeted.

Signed-off-by: George Oldfort <openwrt@10099.de>
Link: https://github.com/openwrt/openwrt/pull/16861
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>