libbpf: Fix unneeded extra initialization in bpf_map_batch_common

bpf_attr doesn't required to be declared with '= {}' as memset is used
in the code.

Fixes: 2ab3d86e ("libbpf: Add libbpf support to batch ops")
Reported-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Brian Vazquez <brianvv@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200116045918.75597-1-brianvv@google.com

tools/lib/bpf/bpf.c

@@ -457,7 +457,7 @@ static int bpf_map_batch_common(int cmd, int fd, void  *in_batch,
 				__u32 *count,
 				const struct bpf_map_batch_opts *opts)
 {
-	union bpf_attr attr = {};
+	union bpf_attr attr;
 	int ret;
 
 	if (!OPTS_VALID(opts, bpf_map_batch_opts))