Merge branch 'net-dsa-lantiq_gswip-two-fixes-for-net-stable'

Martin Blumenstingl says:

====================
net: dsa: lantiq_gswip: two fixes for -net/-stable

While testing the lantiq_gswip driver in OpenWrt at least one board had
a non-working Ethernet port connected to an internal 100Mbit/s PHY22F
GPHY. The problem which could be observed:
- the PHY would detect the link just fine
- ethtool stats would see the TX counter rise
- the RX counter in ethtool was stuck at zero

It turns out that two independent patches are needed to fix this:
- first we need to enable the MII data lines also for internal PHYs
- second we need to program the GSWIP_MII_CFG registers for all ports
  except the CPU port

These two patches have also been tested by back-porting them on top of
Linux 5.4.86 in OpenWrt.

Special thanks to Hauke for debugging and brainstorming this on IRC
with me!
====================

Link: https://lore.kernel.org/r/20210103012544.3259029-1-martin.blumenstingl@googlemail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>