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/xfi3_defconfig b/configs/xfi3_defconfig
index bc95e19..c529f2f 100644
--- a/configs/xfi3_defconfig
+++ b/configs/xfi3_defconfig
@@ -31,6 +31,7 @@
 CONFIG_CMD_FAT=y
 CONFIG_ENV_OVERWRITE=y
 CONFIG_SYS_RELOC_GD_ENV_ADDR=y
+CONFIG_NETCONSOLE=y
 CONFIG_MXS_GPIO=y
 CONFIG_MMC_MXS=y
 CONFIG_CONS_INDEX=0