Convert CONFIG_SYS_FAULT_ECHO_LINK_DOWN to Kconfig

This converts the following to Kconfig:
   CONFIG_SYS_FAULT_ECHO_LINK_DOWN

Cc: Ramon Fried <rfried.dev@gmail.com>
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/ds109_defconfig b/configs/ds109_defconfig
index b007320..8152964 100644
--- a/configs/ds109_defconfig
+++ b/configs/ds109_defconfig
@@ -39,6 +39,7 @@
 CONFIG_ENV_SPI_MAX_HZ=50000000
 CONFIG_ENV_ADDR=0x3D0000
 CONFIG_NETCONSOLE=y
+CONFIG_SYS_FAULT_ECHO_LINK_DOWN=y
 CONFIG_DM=y
 CONFIG_SYS_ATA_STRIDE=4
 CONFIG_SYS_ATA_DATA_OFFSET=0x100