um: get rid of pointless include "..." where include <...> will do

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Richard Weinberger <richard@nod.at>
diff --git a/arch/um/drivers/umcast.h b/arch/um/drivers/umcast.h
index 6f8c0fe..c190c64 100644
--- a/arch/um/drivers/umcast.h
+++ b/arch/um/drivers/umcast.h
@@ -6,7 +6,7 @@
 #ifndef __DRIVERS_UMCAST_H
 #define __DRIVERS_UMCAST_H
 
-#include "net_user.h"
+#include <net_user.h>
 
 struct umcast_data {
 	char *addr;