ramips: mt76x8: fix bogus mediatek,portmap

ramips: mt76x8: fix bogus mediatek,portmap

mt76x8 uses esw_rt3050 driver, which does not accept mediatek,portmap with
string values. Convert the strings to integers to make it work.

According to its switch setup, WRTnode 2P/2R have a WAN port at port 0,
so the correct value should be 0x3e.

tplink_8m.dtsi uses "llllw", but it does not match switch setups of any
device using the DTSI. Remove it from the DTSI and add correct value to DTS
for each device.

These devices have a WAN port at port 0. Set the value to 0x3e.
- tplink,archer-c20-v4
- tplink,archer-c50-v3
- tplink,tl-mr3420-v5
- tplink,tl-wr840n-v4
- tplink,tl-wr841n-v13
- tplink,tl-wr842n-v5

These devices have only one ethernet port. They don't need portmap setting.
- tplink,tl-wa801nd-v5
- tplink,tl-wr802n-v4
- tplink,tl-wr902ac-v3

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