ddr: marvell: a38x: old: Fix some compiler warning of the old code

Fix some compilation warning in the old DDR training code.

Signed-off-by: Marek BehĂșn <kabel@kernel.org>
diff --git a/drivers/ddr/marvell/a38x/old/ddr3_training.c b/drivers/ddr/marvell/a38x/old/ddr3_training.c
index c5ebd7c..29b31a0 100644
--- a/drivers/ddr/marvell/a38x/old/ddr3_training.c
+++ b/drivers/ddr/marvell/a38x/old/ddr3_training.c
@@ -8,6 +8,7 @@
 #include <asm/io.h>
 #include <asm/arch/cpu.h>
 #include <asm/arch/soc.h>
+#include <linux/delay.h>
 
 #include "ddr3_init.h"