fsl/fman: Add fibre support

Set SUPPORTED_FIBRE to mac_dev->if_support. It allows proper usage of
PHYs with optical/fiber support.

Signed-off-by: Maxim Kochetkov <fido_max@inbox.ru>
Acked-by: Madalin Bucur <madalin.bucur@oss.nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>