dpaa2-mac: configure the SerDes phy on a protocol change

This patch integrates the dpaa2-eth driver with the generic PHY
infrastructure in order to search, find and reconfigure the SerDes lanes
in case of a protocol change.

On the .mac_config() callback, the phy_set_mode_ext() API is called so
that the Lynx 28G SerDes PHY driver can change the lane's configuration.
In the same phylink callback the MC firmware is called so that it
reconfigures the MAC side to run using the new protocol.

The consumer drivers - dpaa2-eth and dpaa2-switch - are updated to call
the dpaa2_mac_start/stop functions newly added which will
power_on/power_off the associated SerDes lane.

Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>