realtek: pcs: rtl839x: add initialization patch sequence

realtek: pcs: rtl839x: add initialization patch sequence

Add a patch sequence needed to properly initialize 10G SerDes. This is
taken from the SDK mostly as-is ([1]).

Exit early from SerDes reset for now because it seems to cause some
issues on lower 5G SerDes.

[1] https://github.com/plappermaul/realtek-doc/blob/30e7d6c8c246d66538dc1288986b84674e23dcac/sources/rtk-dms1250/src/dal/cypress/dal_cypress_construct.c#L215

Co-authored-by: Markus Stockhausen <markus.stockhausen@gmx.de>
Signed-off-by: Jonas Jelonek <jelonek.jonas@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/21360
Signed-off-by: Stijn Tintel <stijn@linux-ipv6.be>