perf unwind: Suppress massive unsupported target platform errors

When cross-analyzing perf data recorded on an another platform, massive
unsupported target platform errors are printed. So let's show this message
as warning and only once.

Signed-off-by: Changbin Du <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Hui Wang <[email protected]>
Cc: Ian Rogers <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

Author: Changbin Du

tools/perf/util/unwind-libunwind.c

@@ -56,7 +56,7 @@ int unwind__prepare_access(struct maps *maps, struct map *map, bool *initialized
 	}
 
 	if (!ops) {
-		pr_err("unwind: target platform=%s is not supported\n", arch);
+		pr_warning_once("unwind: target platform=%s is not supported\n", arch);
 		return 0;
 	}
 out_register: