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/umid.c b/arch/um/kernel/umid.c
index f6cc3bd..10bf4ac 100644
--- a/arch/um/kernel/umid.c
+++ b/arch/um/kernel/umid.c
@@ -16,14 +16,14 @@
 	int err;
 
 	if (umid_inited) {
-		printf("umid already set\n");
+		os_warn("umid already set\n");
 		return 0;
 	}
 
 	*add = 0;
 	err = set_umid(name);
 	if (err == -EEXIST)
-		printf("umid '%s' already in use\n", name);
+		os_warn("umid '%s' already in use\n", name);
 	else if (!err)
 		umid_inited = 1;