perf bpf: Add syscall_exit() helper

So that we can hook to the syscalls:sys_exit_SYSCALL tracepoints in
addition to the syscalls:sys_enter_SYSCALL we hook using the
syscall_enter() helper.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: https://lkml.kernel.org/n/tip-6qh8aph1jklyvdu7w89c0izc@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/include/bpf/bpf.h

@@ -26,6 +26,9 @@ struct bpf_map {
 #define syscall_enter(name) \
 	SEC("syscalls:sys_enter_" #name) syscall_enter_ ## name
 
+#define syscall_exit(name) \
+	SEC("syscalls:sys_exit_" #name) syscall_exit_ ## name
+
 #define license(name) \
 char _license[] SEC("license") = #name; \
 int _version SEC("version") = LINUX_VERSION_CODE;