Fix typo in register for the serdes global config.
Fixes: ddb0cd276c ("kernel: rtl8261n: add support for Serdes TX swap")
Signed-off-by: Richard Huynh <voxlympha@gmail.com>
[ add commit description ]
Link: https://github.com/openwrt/openwrt/pull/20465
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>