selftests/bpf: Fix realloc size in bpf_get_addrs

We will segfault once we call realloc in bpf_get_addrs due to
wrong size argument.

Fixes: 6302bde ("selftests/bpf: Add a kprobe_multi subtest to use addrs instead of syms")
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Author: olsajiri

tools/testing/selftests/bpf/trace_helpers.c

@@ -732,7 +732,7 @@ int bpf_get_addrs(unsigned long **addrsp, size_t *cntp, bool kernel)
 
 		if (cnt == max_cnt) {
 			max_cnt += inc_cnt;
-			tmp_addrs = realloc(addrs, max_cnt);
+			tmp_addrs = realloc(addrs, max_cnt * sizeof(long));
 			if (!tmp_addrs) {
 				err = -ENOMEM;
 				goto error;