fec: Revert "fec: Do not assume that PHY reset is active low"

In order to keep DT compatibility we need to revert this, otherwise the original
dts files will no longer work with this driver change.

This reverts commit 7a399e3a.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>