net: mvmdio: add select PHYLIB

net: mvmdio: add select PHYLIB

The mvmdio driver uses the phylib API, so it should select the PHYLIB
symbol, otherwise, a build with mvmdio (but without mvneta) fails to
build with undefined symbols such as mdiobus_unregister, mdiobus_free,
etc.

The mvneta driver does not use the phylib API directly, so it does not
need to select PHYLIB. It already selects the mvmdio driver anyway.

Historically, this problem is due to the fact that the PHY handling
was originally part of mvneta, and was later moved to a separate
driver, without updating the Kconfig select statements
accordingly. And since there was no functional reason to use mvmdio
without mvneta, this case was not tested.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>