net: mvpp2: some AN fields require the link to be down when updated

The GMAC configuration helper modifies values in the auto-negotiation
register. Some of its values require the port to be forced down when
modifying their values. This patches fixes the check made on the bit to
be updated in this register, so that the port is forced down when
needed. This fix cases where some of those parameters were updated, but
not taken into account, such as when using RGMII interfaces.

Fixes: d14e078f ("net: marvell: mvpp2: only reprogram what is necessary on mac_config")
Signed-off-by: Antoine Tenart <antoine.tenart@bootlin.com>
Signed-off-by: David S. Miller <davem@davemloft.net>