net: ethernet: Fix SGMII unable to switch speed and autonego failure

TSE PCS SGMII ethernet has an issue where switching speed doesn't work
caused by a faulty register macro offset. This fixes the issue.

Signed-off-by: Jia Jie Ho <ho.jia.jie@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>