selftests/bpf: Fix btf_dump padding test case

Existing padding test case for btf_dump has a good test that was
supposed to test padding generation at the end of a struct, but its
expected output was specified incorrectly. Fix this.

Fixes: 2d2a3ad8 ("selftests/bpf: add btf_dump BTF-to-C conversion tests")
Reported-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20191008231009.2991130-4-andriin@fb.com

tools/testing/selftests/bpf/progs/btf_dump_test_case_padding.c

@@ -62,6 +62,10 @@ struct padded_a_lot {
  *	long: 64;
  *	long: 64;
  *	int b;
+ *	long: 32;
+ *	long: 64;
+ *	long: 64;
+ *	long: 64;
  *};
  *
  */
@@ -95,7 +99,6 @@ struct zone_padding {
 struct zone {
 	int a;
 	short b;
-	short: 16;
 	struct zone_padding __pad__;
 };