Bump firmware build to incorporate usb improvements

Author: johnnyman727

package/tessel/tools/Makefile

@@ -7,7 +7,7 @@ PKG_RELEASE=$(PKG_SOURCE_VERSION)
 PKG_SOURCE_PROTO:=git
 PKG_SOURCE_URL:=https://github.com/tessel/v2-samd21.git
 PKG_SOURCE_SUBDIR:=$(PKG_NAME)-$(PKG_VERSION)
-PKG_SOURCE_VERSION:=b893412962af02522045e5000dac23c1b65c5874
+PKG_SOURCE_VERSION:=c20b3ca9a461783842f706866156b2407a652cca
 PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION)-$(PKG_SOURCE_VERSION).tar.gz
 
 include $(INCLUDE_DIR)/package.mk