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/devkit3250_defconfig b/configs/devkit3250_defconfig
index 2210fab..2a24e01 100644
--- a/configs/devkit3250_defconfig
+++ b/configs/devkit3250_defconfig
@@ -44,6 +44,7 @@
 CONFIG_USE_BOOTFILE=y
 CONFIG_BOOTFILE="uImage"
 CONFIG_VERSION_VARIABLE=y
+CONFIG_SYS_FAULT_ECHO_LINK_DOWN=y
 CONFIG_DMA_LPC32XX=y
 CONFIG_LPC32XX_GPIO=y
 CONFIG_SYS_I2C_LEGACY=y