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/M53017EVB_defconfig b/configs/M53017EVB_defconfig
index b8292fd..b12e181 100644
--- a/configs/M53017EVB_defconfig
+++ b/configs/M53017EVB_defconfig
@@ -21,6 +21,7 @@
 CONFIG_CMD_DATE=y
 CONFIG_ENV_IS_IN_FLASH=y
 CONFIG_ENV_ADDR=0x40000
+CONFIG_SYS_FAULT_ECHO_LINK_DOWN=y
 CONFIG_UDP_CHECKSUM=y
 CONFIG_SYS_I2C_LEGACY=y
 CONFIG_SYS_I2C_FSL=y