perf trace: Enclose strings with double quotes

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

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>
Cc: Wang Nan <wangnan0@huawei.com>
Link: https://lkml.kernel.org/n/tip-jab52t1dcuh6vlztqle9g7u9@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-trace.c

@@ -1149,7 +1149,7 @@ static size_t syscall_arg__scnprintf_augmented_string(struct syscall_arg *arg, 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,