net: phy: remove unused functions phy_package_[read|write]_mmd

These functions have never had a user, so remove them.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/5792e2cd-6f0a-4f7d-a5ef-b932f94d82f3@gmail.com


Signed-off-by: Paolo Abeni <pabeni@redhat.com>