serial: constify serial_assign()

Signed-off-by: Gerlando Falauto <gerlando.falauto@keymile.com>
Acked-by: Mike Frysinger <vapier@gentoo.org>
diff --git a/common/serial.c b/common/serial.c
index 03bbb19..75cc1bb 100644
--- a/common/serial.c
+++ b/common/serial.c
@@ -149,7 +149,7 @@
 	}
 }
 
-int serial_assign(char *name)
+int serial_assign(const char *name)
 {
 	struct serial_device *s;