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/guruplug_defconfig b/configs/guruplug_defconfig
index 5833f12..f7e934b 100644
--- a/configs/guruplug_defconfig
+++ b/configs/guruplug_defconfig
@@ -36,6 +36,7 @@
 CONFIG_ENV_OVERWRITE=y
 CONFIG_ENV_IS_IN_NAND=y
 CONFIG_SYS_RELOC_GD_ENV_ADDR=y
+CONFIG_NETCONSOLE=y
 CONFIG_DM=y
 CONFIG_MVSATA_IDE=y
 CONFIG_BLK=y