liebherr: Drop duplicate dm.h inclusion

We only need to include this header once. Drop the duplicate.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/board/liebherr/display5/display5.c b/board/liebherr/display5/display5.c
index ada7cf5..5f44714 100644
--- a/board/liebherr/display5/display5.c
+++ b/board/liebherr/display5/display5.c
@@ -27,7 +27,6 @@
 #include <i2c.h>
 #include <linux/delay.h>
 
-#include <dm.h>
 #include <dm/platform_data/serial_mxc.h>
 #include <dm/platdata.h>