uVisor importer script: Point to the dev branch

Author: AlessandroA

features/FEATURE_UVISOR/importer/Makefile

@@ -33,7 +33,7 @@ TARGET_LIB_INC:=$(TARGET_PREFIX)includes/uvisor-lib
 
 # uVisor source directory - hidden from mbed via TARGET_IGNORE
 UVISOR_GIT_URL:=https://github.com/ARMmbed/uvisor
-UVISOR_GIT_BRANCH:=unstable
+UVISOR_GIT_BRANCH:=dev
 UVISOR_DIR:=TARGET_IGNORE/uvisor
 UVISOR_API:=$(UVISOR_DIR)/api
 UVISOR_GIT_CFG=$(UVISOR_DIR)/.git/config