Revert "ethernet: T5566: disable energy efficient ethernet (EEE) for interfaces"

This reverts commit ab30509b25d54dac99294b76ba03fd49c3d2c946.

As in T6152 there seem to be some NICs that have a non working implementation
of reading the EEE registers. Remove this feature in the meantime until there
is a less exploding solution hindering boards to boot.

Return to Kernel defaults by removing this code path.

(cherry picked from commit 946f93778f15f4af9f31cd5b164efcd931693635)