net: dsa: felix: set TX flow control according to the phylink_mac_link_up resolution

Instead of relying on the static initialization done by ocelot_init_port()
which enables flow control unconditionally, set SYS_PAUSE_CFG_PAUSE_ENA
according to the parameters negotiated by the PHY.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>