net: fec_ptp: Use dev_err() instead of pr_err()

dev_err() is more appropriate for printing error messages inside
drivers, so switch to dev_err().

Signed-off-by: Fabio Estevam <festevam@gmail.com>
Acked-by: Fugang Duan <fugang.duan@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>