realtek: dts: add Netgear GS110TPP serdes for port 9/10

realtek: dts: add Netgear GS110TPP serdes for port 9/10

The Netgear GS110TPP uses an RTL8214C to drive ports 9 and 10. The
DTS is missing the corresponding serdes assignment. From looking at
[1] it seems to be connected to pins 82-85 (serdes 2). Add that
definition. With that the last improper use of SWITCH_PORT() macro
is sorted out.

Remark: I do not own this device. The patch just resembles what
the picture [1] shows.

[1] https://svanheule.net/switches/_media/wiki/gs110tpp-top.jpg

Signed-off-by: Markus Stockhausen <markus.stockhausen@gmx.de>
Link: https://github.com/openwrt/openwrt/pull/22232
Signed-off-by: Robert Marko <robimarko@gmail.com>