[PATCH] bpf: Fix compile warnings when !CONFIG_BPF_SYSCALL

[Jason Gunthorpe]

Such as:

In file included from ./include/trace/events/xdp.h:10:0,
                 from ./include/linux/bpf_trace.h:6,
                 from drivers/net/ethernet/intel/i40e/i40e_txrx.c:29:
./include/trace/events/xdp.h:94:17: warning: ‘struct bpf_map’ declared inside 
parameter list
    const struct bpf_map *map, u32 map_index),
                 ^

By adding a forward declaration for struct bpf_map. In the
CONFIG_BPF_SYSCALL case the declaration comes in via
trace/events/bpf.h

Fixes: 59a308967589 ("xdp: separate xdp_redirect tracepoint in map case")
Signed-off-by: Jason Gunthorpe <j...@mellanox.com>
---
 include/trace/events/xdp.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/include/trace/events/xdp.h b/include/trace/events/xdp.h
index 4cd0f05d01134d..36b2a9043189be 100644
--- a/include/trace/events/xdp.h
+++ b/include/trace/events/xdp.h
@@ -9,6 +9,8 @@
 #include <linux/filter.h>
 #include <linux/tracepoint.h>
 
+struct bpf_map;
+
 #define __XDP_ACT_MAP(FN)      \
        FN(ABORTED)             \
        FN(DROP)                \
-- 
2.7.4