net: phy: remove device_phy_find_device

AFAICS this function has never had a user.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/ab7b8094-2eea-4e82-a047-fd60117f220b@gmail.com


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