net: mdio_bus: validate "addr" for mdiobus_is_registered_device()

mdiobus_is_registered_device() doesn't checking that "addr" was valid
before dereferencing bus->mdio_map[]. Extract the code that checks
this from mdiobus_get_phy(), and use it here as well.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://lore.kernel.org/r/E1qNxvu-00111m-1V@rmk-PC.armlinux.org.uk


Signed-off-by: Jakub Kicinski <kuba@kernel.org>