MII: fix Kconfig dependencies for MII

MII Kconfig option is apart of the core networking drivers and
by default NET_CORE is enabled so drivers selecting MII will
have MII enabled as well.  It was found using the randconfig
option during testing, MII would be selected but NET_CORE
could be disabled.  This caused a dependency error.

Resolved the dependency by selecting NET_CORE when MII is
selected.

Reported-by: Emil Tantilov <emil.s.tantilov@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ethernet/broadcom/Kconfig b/drivers/net/ethernet/broadcom/Kconfig
index d82ad22..f15e72e 100644
--- a/drivers/net/ethernet/broadcom/Kconfig
+++ b/drivers/net/ethernet/broadcom/Kconfig
@@ -22,6 +22,7 @@
 	tristate "Broadcom 440x/47xx ethernet support"
 	depends on SSB_POSSIBLE && HAS_DMA
 	select SSB
+	select NET_CORE
 	select MII
 	---help---
 	  If you have a network (Ethernet) controller of this type, say Y
@@ -53,6 +54,7 @@
 config BCM63XX_ENET
 	tristate "Broadcom 63xx internal mac support"
 	depends on BCM63XX
+	select NET_CORE
 	select MII
 	select PHYLIB
 	help