perf include bpf: Add bpf_tail_call() prototype

Will be used together with BPF_MAP_TYPE_PROG_ARRAY in
tools/perf/examples/bpf/augmented_raw_syscalls.c.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Luis Cláudio Gonçalves <lclaudio@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/n/tip-pd1bpy8i31nta6jqwdex871g@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/include/bpf/bpf.h

@@ -45,6 +45,8 @@ struct ____btf_map_##name __attribute__((section(".maps." #name), used)) \
 static int (*bpf_map_update_elem)(struct bpf_map *map, void *key, void *value, u64 flags) = (void *)BPF_FUNC_map_update_elem;
 static void *(*bpf_map_lookup_elem)(struct bpf_map *map, void *key) = (void *)BPF_FUNC_map_lookup_elem;
 
+static void (*bpf_tail_call)(void *ctx, void *map, int index) = (void *)BPF_FUNC_tail_call;
+
 #define SEC(NAME) __attribute__((section(NAME),  used))
 
 #define probe(function, vars) \