net: phy: realtek: add RTL8224 polarity support

net: phy: realtek: add RTL8224 polarity support

The RTL8224 has a register to configure the polarity of every pair of
each port. It provides device designers more flexbility when wiring the
chip.

Unfortunately, the register is left in an unknown state after a reset.
Thus on devices where the bootloader don't initialize it, the driver has
to do it to detect and use a link.

The MDI polarity swap can be set in the device tree using the property
enet-phy-pair-polarity. The u32 value is a bitfield where bit[0..3]
control the polarity of pairs A..D.

Signed-off-by: Damien Dejean <dam.dejean@gmail.com>
Link: https://patch.msgid.link/20260318215502.106528-5-dam.dejean@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>