net: phy: Re-parent menus for MDIO bus drivers correctly

After 90eff909 ("net: phy: Allow splitting MDIO bus/device support
from PHYs") the various MDIO bus drivers were no longer parented with
config PHYLIB but with config MDIO_BUS which is not a menuconfig, fix
this by depending on MDIO_DEVICE which is a menuconfig.

This is visually nicer and less confusing for users.

Fixes: 90eff909 ("net: phy: Allow splitting MDIO bus/device support from PHYs")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/phy/Kconfig

@@ -7,6 +7,8 @@ menuconfig MDIO_DEVICE
 	help
 	  MDIO devices and driver infrastructure code.
 
+if MDIO_DEVICE
+
 config MDIO_BUS
 	tristate
 	default m if PHYLIB=m
@@ -179,6 +181,7 @@ config MDIO_XGENE
 	  APM X-Gene SoC's.
 
 endif
+endif
 
 config PHYLINK
 	tristate