kernel/trace/bpf_trace.c: work around gcc-4.4.4 anon union initialization bug

kernel/trace/bpf_trace.c: In function 'bpf_event_output':
kernel/trace/bpf_trace.c:312: error: unknown field 'next' specified in initializer
kernel/trace/bpf_trace.c:312: warning: missing braces around initializer
kernel/trace/bpf_trace.c:312: warning: (near initialization for 'raw.frag.<anonymous>')

Fixes: 555c8a86 ("bpf: avoid stack copy and use skb ctx for event output")
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

kernel/trace/bpf_trace.c

@@ -309,7 +309,9 @@ u64 bpf_event_output(struct bpf_map *map, u64 flags, void *meta, u64 meta_size,
 	};
 	struct perf_raw_record raw = {
 		.frag = {
+			{
 				.next	= ctx_size ? &frag : NULL,
+			},
 			.size	= meta_size,
 			.data	= meta,
 		},