um: Use os_warn to print out pre-boot warning/error messages

Use os_warn() instead of printf/fprintf to print out
pre-boot warning/error messages to stderr.
Note that the help message and version message are
kept to print out to stdout, because user explicitly
specifies those options to get such information.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Richard Weinberger <richard@nod.at>
diff --git a/arch/um/kernel/um_arch.c b/arch/um/kernel/um_arch.c
index 5df91d8..9c5d111 100644
--- a/arch/um/kernel/um_arch.c
+++ b/arch/um/kernel/um_arch.c
@@ -34,7 +34,7 @@
 static void __init add_arg(char *arg)
 {
 	if (strlen(command_line) + strlen(arg) + 1 > COMMAND_LINE_SIZE) {
-		printf("add_arg: Too many command line arguments!\n");
+		os_warn("add_arg: Too many command line arguments!\n");
 		exit(1);
 	}
 	if (strlen(command_line) > 0)
@@ -126,6 +126,7 @@
 
 static int __init uml_version_setup(char *line, int *add)
 {
+	/* Explicitly use printf() to show version in stdout */
 	printf("%s\n", init_utsname()->release);
 	exit(0);
 
@@ -154,8 +155,8 @@
 
 static int __init no_skas_debug_setup(char *line, int *add)
 {
-	printf("'debug' is not necessary to gdb UML in skas mode - run \n");
-	printf("'gdb linux'\n");
+	os_warn("'debug' is not necessary to gdb UML in skas mode - run\n");
+	os_warn("'gdb linux'\n");
 
 	return 0;
 }
@@ -171,6 +172,7 @@
 
 	printf(usage_string, init_utsname()->release);
 	p = &__uml_help_start;
+	/* Explicitly use printf() to show help in stdout */
 	while (p < &__uml_help_end) {
 		printf("%s", *p);
 		p++;