net: dsa: microchip: split adjust_link() in phylink_mac_link_{up|down}()

The DSA subsystem moved to phylink and adjust_link() became deprecated in
the process. This patch removes adjust_link from the KSZ DSA switches and
adds phylink_mac_link_up() and phylink_mac_link_down().

Signed-off-by: Codrin Ciubotariu <codrin.ciubotariu@microchip.com>
Reviewed-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>