[PATCH bpf-next] selftests/bpf: fix a compilation warning

[Yonghong Song <yhs@xxxxxx>]

The following warning is triggered when I used clang compiler
to build the selftest.

  /.../prog_tests/btf_dedup_split.c:368:6: warning: variable 'btf2' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized]
        if (!ASSERT_OK(err, "btf_dedup"))
            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
  /.../prog_tests/btf_dedup_split.c:424:12: note: uninitialized use occurs here
        btf__free(btf2);
                  ^~~~
  /.../prog_tests/btf_dedup_split.c:368:2: note: remove the 'if' if its condition is always false
        if (!ASSERT_OK(err, "btf_dedup"))
        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  /.../prog_tests/btf_dedup_split.c:343:25: note: initialize the variable 'btf2' to silence this warning
        struct btf *btf1, *btf2;
                               ^
                                = NULL

Initialize local variable btf2 = NULL and the warning is gone.

Signed-off-by: Yonghong Song <yhs@xxxxxx>
---
 tools/testing/selftests/bpf/prog_tests/btf_dedup_split.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/btf_dedup_split.c b/tools/testing/selftests/bpf/prog_tests/btf_dedup_split.c
index 878a864dae3b..90aac437576d 100644
--- a/tools/testing/selftests/bpf/prog_tests/btf_dedup_split.c
+++ b/tools/testing/selftests/bpf/prog_tests/btf_dedup_split.c
@@ -340,7 +340,7 @@ static void btf_add_dup_struct_in_cu(struct btf *btf, int start_id)
 
 static void test_split_dup_struct_in_cu()
 {
-	struct btf *btf1, *btf2;
+	struct btf *btf1, *btf2 = NULL;
 	int err;
 
 	/* generate the base data.. */
-- 
2.30.2