Enable ethtool for its SFP diagnostics mode

Change-Id: I6963e6d3a67864353400882bbf930469b05434e2
diff --git a/configs/czechlight_clearfog_defconfig b/configs/czechlight_clearfog_defconfig
index 32f9764..f569b1f 100644
--- a/configs/czechlight_clearfog_defconfig
+++ b/configs/czechlight_clearfog_defconfig
@@ -37,6 +37,7 @@
 BR2_PACKAGE_SPI_TOOLS=y
 BR2_PACKAGE_UBOOT_TOOLS=y
 BR2_PACKAGE_LIBGPIOD_TOOLS=y
+BR2_PACKAGE_ETHTOOL=y
 BR2_PACKAGE_IPROUTE2=y
 BR2_PACKAGE_NETCONF_CLI=y
 BR2_PACKAGE_BASH=y