perf trace: Enclose strings with double quotes

To match 'strace' output, helping with upcoming regression tests
comparing both outputs.

Cc: Adrian Hunter <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Luis Cláudio Gonçalves <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Wang Nan <[e-mail]>
Link: https://lkml.kernel.org/n/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/builtin-trace.c

···
 {
 	struct augmented_arg *augmented_arg = arg->augmented.args;
 
-	return scnprintf(bf, size, "%.*s", augmented_arg->size, augmented_arg->value);
+	return scnprintf(bf, size, "\"%.*s\"", augmented_arg->size, augmented_arg->value);
 }
 
 static size_t syscall_arg__scnprintf_filename(char *bf, size_t size,