net: mscc: ocelot: split writes to pause frame enable bit and to thresholds

We don't want ocelot_port_set_maxlen to enable pause frame TX, just to
adjust the pause thresholds.

Move the unconditional enabling of pause TX to ocelot_init_port. There
is no good place to put such setting because it shouldn't be
unconditional. But at the moment it is, we're not changing that.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>