fecmxc_initialize_multi change from phy id to phy mask

The fecmxc_initialize_multi now accepts phy address mask instead of a
single phy address.

Modified otherboard that directly uses fecmxc_initialize_multi()

Modified also i.MX6 RXD0/RXD1 pad to pull down (they are also directly
connected to the Atheros 8035/8030 although they should be functional
only in the RMII mode - 8030).

Signed-off-by: Rabeeh Khoury <rabeeh@solid-run.com>