net: phy: add devm/of_phy_package_join helper

Add devm/of_phy_package_join helper to join PHYs in a PHY package. These
are variant of the manual phy_package_join with the difference that
these will use DT nodes to derive the base_addr instead of manually
passing an hardcoded value.

An additional value is added in phy_package_shared, "np" to reference
the PHY package node pointer in specific PHY driver probe_once and
config_init_once functions to make use of additional specific properties
defined in the PHY package node in DT.

The np value is filled only with of_phy_package_join if a valid PHY
package node is found. A valid PHY package node must have the node name
set to "ethernet-phy-package".

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>