realtek: allow different serdes patch sequences

realtek: allow different serdes patch sequences

Prepare the SerDes patch function to allow different patch sequences
depending on the phy mode. Patches are required to allow devices with a
lightweight bootloader (one that doesn't have a "rtk network init"
command) to use the serdes. Some modes required a different patch
sequence than the one currently used.

Signed-off-by: Damien Dejean <dam.dejean@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/19834
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>