drbd: Remove left-over unused define

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
diff --git a/include/linux/drbd_limits.h b/include/linux/drbd_limits.h
index 7f5149b..bcebb01 100644
--- a/include/linux/drbd_limits.h
+++ b/include/linux/drbd_limits.h
@@ -170,5 +170,4 @@
 
 #define DRBD_PROTOCOL_DEF DRBD_PROT_C
 
-#undef RANGE
 #endif