mx53evk: Convert to generic board

Enable CONFIG_SYS_GENERIC_BOARD, so that we get rid of the following warning on
boot:

"Warning: Your board does not use generic board. Please read
doc/README.generic-board and take action. Boards not
upgraded by the late 2014 may break or be removed."

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
diff --git a/include/configs/mx53evk.h b/include/configs/mx53evk.h
index 3f0d80a..5bbae8c 100644
--- a/include/configs/mx53evk.h
+++ b/include/configs/mx53evk.h
@@ -23,6 +23,8 @@
 #define CONFIG_INITRD_TAG
 #define CONFIG_REVISION_TAG
 
+#define CONFIG_SYS_GENERIC_BOARD
+
 #define CONFIG_OF_LIBFDT
 
 /* Size of malloc() pool */