phy: add sgmii and 10gkr modes to the phy_mode enum

This patch adds more generic PHY modes to the phy_mode enum, to
allow configuring generic PHYs to the SGMII and/or the 10GKR mode
by using the set_mode callback.

Signed-off-by: Antoine Tenart <antoine.tenart@free-electrons.com>
Acked-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>