display: Fix warnings

Treat warnings as errors again

Change-Id: Ibd7f484d31ad420b85e82fd5183d70bf7dce4bfa
diff --git a/common.mk b/common.mk
index 44bef71..14d8ded 100644
--- a/common.mk
+++ b/common.mk
@@ -19,8 +19,7 @@
 
 #Common C flags
 common_flags := -DDEBUG_CALC_FPS -Wno-missing-field-initializers
-#TODO: Add -Werror back once all the current warnings are fixed
-common_flags += -Wconversion -Wall
+common_flags += -Wconversion -Wall -Werror
 
 ifeq ($(ARCH_ARM_HAVE_NEON),true)
     common_flags += -D__ARM_HAVE_NEON