net: pcs: pcs-mtk-lynxi: report in-band capability for 2500Base-X

net: pcs: pcs-mtk-lynxi: report in-band capability for 2500Base-X

It turns out that 2500Base-X actually works fine with in-band status on
MediaTek's LynxI PCS -- I wrongly concluded it didn't because it is
broken in all the copper SFP modules and GPON sticks I used for testing.

Hence report LINK_INBAND_ENABLE also for 2500Base-X mode.

This reverts most of commit a003c38d9bbb ("net: pcs: pcs-mtk-lynxi:
correctly report in-band status capabilities").

The removal of the QSGMII interface mode was correct and is left
untouched.

Link: https://github.com/openwrt/openwrt/issues/21436
Fixes: a003c38d9bbb ("net: pcs: pcs-mtk-lynxi: correctly report in-band status capabilities")
Signed-off-by: Daniel Golle <daniel@makrotopia.org>
Link: https://patch.msgid.link/b1cf26157b63fee838be09ae810497fb22fd8104.1768961746.git.daniel@makrotopia.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>