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/SBx81LIFKW_defconfig b/configs/SBx81LIFKW_defconfig
index f5143b2..a1abbc1 100644
--- a/configs/SBx81LIFKW_defconfig
+++ b/configs/SBx81LIFKW_defconfig
@@ -30,6 +30,7 @@
 CONFIG_USE_ENV_SPI_MAX_HZ=y
 CONFIG_ENV_SPI_MAX_HZ=20000000
 CONFIG_SYS_RELOC_GD_ENV_ADDR=y
+CONFIG_NETCONSOLE=y
 CONFIG_DM=y
 CONFIG_DM_PCA953X=y
 CONFIG_DM_I2C=y