drivers: mdio: mdio nxp s32 netc should depend on eth netc driver

MDIO is currently initialized in the ETH NXP S32 NETC
driver for Physical Station Interface (PSI), so do not
try to build the MDIO driver if the ETH driver is not built

Signed-off-by: Dat Nguyen Duy <dat.nguyenduy@nxp.com>