net: phy: add support for a common probe between shared PHYs

Shared PHYs (PHYs in the same hardware package) may have shared
registers and their drivers would usually need to share information.
There is currently a way to have a shared (part of the) init, by using
phy_package_init_once(). This patch extends the logic to share parts of
the probe to allow sharing the initialization of locks or resources
retrieval.

Signed-off-by: Antoine Tenart <antoine.tenart@bootlin.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>