Convert CONFIG_NETCONSOLE to Kconfig

This converts the following to Kconfig:
   CONFIG_NETCONSOLE

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/net2big_v2_defconfig b/configs/net2big_v2_defconfig
index 13e7956..e2e8341 100644
--- a/configs/net2big_v2_defconfig
+++ b/configs/net2big_v2_defconfig
@@ -40,6 +40,7 @@
 CONFIG_USE_ENV_SPI_MAX_HZ=y
 CONFIG_ENV_SPI_MAX_HZ=20000000
 CONFIG_ENV_ADDR=0x70000
+CONFIG_NETCONSOLE=y
 CONFIG_DM=y
 CONFIG_SATA_MV=y
 CONFIG_BLK=y