realtek: pcs: rtl931x: soften early exit for USXGMII

realtek: pcs: rtl931x: soften early exit for USXGMII

Now that the PCS driver keeps track of how many links are registered per
SerDes, we can also decide which real hardware mode to use when USXGMII
is set. While there is still no proper setup for 10G-QXGMII or XSGMII,
the existing USXGMII 10G-SXGMII setup seems to work properly.

Soften the condition when to exit early so that single 10G port USXGMII
can be setup properly.

Fixes: c18476d0c581 ("realtek: RTL931x: disable USXGMII SerDes setup")
Signed-off-by: Jonas Jelonek <jelonek.jonas@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/21365
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>