[PATCH bpf-next] selftests/bpf: Fix uninitialized duration warning

[Joe Stringer]

Daniel Borkmann reports:

test_progs.c: In function ‘main’:
test_progs.c:81:3: warning: ‘duration’ may be used uninitialized in this 
function [-Wmaybe-uninitialized]
   printf("%s:PASS:%s %d nsec\n", __func__, tag, duration);\
   ^~~~~~
test_progs.c:1706:8: note: ‘duration’ was declared here
  __u32 duration;
        ^~~~~~~~

Signed-off-by: Joe Stringer <j...@wand.net.nz>
---

I'm actually not able to reproduce this with GCC 7.3 or 8.2, so I'll
rely on review to establish that this patch works as intended.
---
 tools/testing/selftests/bpf/test_progs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/bpf/test_progs.c 
b/tools/testing/selftests/bpf/test_progs.c
index 2d3c04f45530..c1e688f61061 100644
--- a/tools/testing/selftests/bpf/test_progs.c
+++ b/tools/testing/selftests/bpf/test_progs.c
@@ -1703,7 +1703,7 @@ static void test_reference_tracking()
        const char *file = "./test_sk_lookup_kern.o";
        struct bpf_object *obj;
        struct bpf_program *prog;
-       __u32 duration;
+       __u32 duration = 0;
        int err = 0;
 
        obj = bpf_object__open(file);
-- 
2.17.1