Fix warnings from of_data copy fix

Forgot to cast of_flat_tree to ulong.

Signed-off-by: Andy Fleming <afleming@freescale.com>
diff --git a/common/cmd_bootm.c b/common/cmd_bootm.c
index 90e3f8b..bcb927f 100644
--- a/common/cmd_bootm.c
+++ b/common/cmd_bootm.c
@@ -932,7 +932,7 @@
 	 * so we flag it to be copied if it is not.
 	 */
 	if (of_flat_tree >= (char *)CFG_BOOTMAPSZ)
-		of_data = of_flat_tree;
+		of_data = (ulong)of_flat_tree;
 #endif
 
 	/* move of_flat_tree if needed */
@@ -993,7 +993,7 @@
 	 * so we flag it to be copied if it is not.
 	 */
 	if (of_flat_tree >= (char *)CFG_BOOTMAPSZ)
-		of_data = of_flat_tree;
+		of_data = (ulong)of_flat_tree;
 #endif
 
 	/* move of_flat_tree if needed */