net: mdio: mux-meson-gxl: set reversed bit when using internal phy

net: mdio: mux-meson-gxl: set reversed bit when using internal phy

This bit is necessary to receive packets from the internal PHY.
Without this bit set, no activity occurs on the interface.

Normally u-boot sets this bit, but if u-boot is compiled without
net support, the interface will be up but without any activity.

The vendor SDK sets this bit along with the PHY_ID bits.

Ported from the Linux change at [1] from Da Xu merged in
commit [2].

[1] https://lore.kernel.org/all/20250425192009.1439508-1-da@libre.computer/
[2] b23285e93bef ("net: mdio: mux-meson-gxl: set reversed bit when using internal phy")

Suggested-by: Da Xue <da@libre.computer>
Link: https://lore.kernel.org/r/20250502-u-boot-topic-mdio-mux-gxl-bit28-v1-1-399f6c3db154@linaro.org
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>