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>

arch/um/kernel/exec.c

@@ -12,10 +12,10 @@
 #include <asm/current.h>
 #include <asm/processor.h>
 #include <asm/uaccess.h>
-#include "as-layout.h"
-#include "mem_user.h"
-#include "skas.h"
-#include "os.h"
+#include <as-layout.h>
+#include <mem_user.h>
+#include <skas.h>
+#include <os.h>
 #include "internal.h"
 
 void flush_thread(void)