perf trace: Mark the 'head' arg in the set_robust_list syscall as coming from user space

With that it uses the generic BTF based pretty printer:

This one we need to think about, not being acquainted with this syscall,
should we _traverse_ that list somehow? Would that be useful?

  root@number:~# perf trace -e set_robust_list sleep 1
       0.000 ( 0.004 ms): sleep/1206493 set_robust_list(head: (struct robust_list_head){.list = (struct robust_list){.next = (struct robust_list *)0x7f48a9a02a20,},.futex_offset = (long int)-32,}, len: 24) =
  root@number:~#

strace prints the default integer args:

  root@number:~# strace -e set_robust_list sleep 1
  set_robust_list(0x7efd99559a20, 24)     = 0
  +++ exited with 0 +++
  root@number:~#

Cc: Adrian Hunter <[email protected]>
Cc: Alan Maguire <[email protected]>
Cc: Howard Chu <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Kan Liang <[email protected]>
Cc: Namhyung Kim <[email protected]
Link: https://lore.kernel.org/lkml/ZuH6MquMraBvODRp@x1
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

Author: acmel

tools/perf/builtin-trace.c

@@ -1351,6 +1351,8 @@ static const struct syscall_fmt syscall_fmts[] = {
 	{ .name	    = "sendto",
 	  .arg = { [3] = { .scnprintf = SCA_MSG_FLAGS, /* flags */ },
 		   [4] = SCA_SOCKADDR_FROM_USER(addr), }, },
+	{ .name	    = "set_robust_list",	    .errpid = true,
+	  .arg = { [0] = { .from_user = true /* head */, }, }, },
 	{ .name	    = "set_tid_address", .errpid = true, },
 	{ .name	    = "setitimer",
 	  .arg = { [0] = STRARRAY(which, itimers), }, },