perf help: Elliminate dup code for reporting

And switch from warning() to pr_warning(), to elliminate another
duplication: too many error reporting facilities.

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: http://lkml.kernel.org/n/tip-pkzcjrhek3uuqc4i5i9ealwd@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-help.c

@@ -210,6 +210,12 @@ static void do_add_man_viewer_info(const char *name,
 	man_viewer_info_list = new;
 }
 
+static void unsupported_man_viewer(const char *name, const char *var)
+{
+	pr_warning("'%s': path for unsupported man viewer.\n"
+		   "Please consider using 'man.<tool>.%s' instead.", name, var);
+}
+
 static int add_man_viewer_path(const char *name,
 			       size_t len,
 			       const char *value)
@@ -217,9 +223,7 @@ static int add_man_viewer_path(const char *name,
 	if (supported_man_viewer(name, len))
 		do_add_man_viewer_info(name, len, value);
 	else
-		warning("'%s': path for unsupported man viewer.\n"
-			"Please consider using 'man.<tool>.cmd' instead.",
-			name);
+		unsupported_man_viewer(name, "cmd");
 
 	return 0;
 }
@@ -229,9 +233,7 @@ static int add_man_viewer_cmd(const char *name,
 			      const char *value)
 {
 	if (supported_man_viewer(name, len))
-		warning("'%s': cmd for supported man viewer.\n"
-			"Please consider using 'man.<tool>.path' instead.",
-			name);
+		unsupported_man_viewer(name, "path");
 	else
 		do_add_man_viewer_info(name, len, value);