realtek: add serdes patch for 10G_QXGMII

realtek: add serdes patch for 10G_QXGMII

Adds the serdes patch sequence [1] and configuration [2] for the
PHY_INTERFACE_MODE_10G_QXGMII mode (aka USXGMII_QX in Realtek sources).
It is required by devices with light bootloaders (ie not u-boot) that
does not initialize the hardware before booting the kernel.

[1] https://github.com/ddejean/dms-1250-oss-release/blob/main/sdk/sdk_rtk_switch/rtk-sdk/src/dal/longan/dal_longan_construct.c#L1075
[2] https://github.com/ddejean/dms-1250-oss-release/blob/main/sdk/sdk_rtk_switch/rtk-sdk/src/dal/longan/dal_longan_construct.c#L1315

Signed-off-by: Damien Dejean <dam.dejean@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/20472
Signed-off-by: Robert Marko <robimarko@gmail.com>