tests: fix setting gcov flag for test-cov target

Type: fix

Change-Id: I3c663babe4f32f5d2870265336b5d272cc029ce7
Signed-off-by: Dave Wallace <dwallacelf@gmail.com>
diff --git a/test/Makefile b/test/Makefile
index 27e7501..2eb2ef3 100644
--- a/test/Makefile
+++ b/test/Makefile
@@ -200,7 +200,7 @@
 endif
 
 ARG7=
-ifneq ($(findstring $(TESTS_GCOV),1 y yes),)
+ifneq ($(findstring $(TEST_GCOV),1 y yes),)
 ARG7=--gcov
 endif