Use the userspace RSTP implementation for fast convergence

This appear to work, yay. It is also (the RSTP protocol) what the
OpenROADM specification mandates.

Change-Id: I87da50af203da3c1df137f281a017eb236a451dc
diff --git a/configs/czechlight_clearfog_defconfig b/configs/czechlight_clearfog_defconfig
index 78a9b65..deadb2f 100644
--- a/configs/czechlight_clearfog_defconfig
+++ b/configs/czechlight_clearfog_defconfig
@@ -41,6 +41,7 @@
 BR2_PACKAGE_SPI_TOOLS=y
 BR2_PACKAGE_UBOOT_TOOLS=y
 BR2_PACKAGE_LIBGPIOD_TOOLS=y
+BR2_PACKAGE_MSTPD=y
 BR2_PACKAGE_ETHTOOL=y
 BR2_PACKAGE_IPROUTE2=y
 BR2_PACKAGE_NETCONF_CLI=y