am335x: disable internal delay for RGMII mode

According to errata the AM335x device does not support internal delay
mode, so RGMII1_IDMODE and RGMII2_IDMODE must be set to 1.

Signed-off-by: Yegor Yefremov <yegorslists@googlemail.com>
diff --git a/board/ti/am335x/board.c b/board/ti/am335x/board.c
index 6908378..135f1a2 100644
--- a/board/ti/am335x/board.c
+++ b/board/ti/am335x/board.c
@@ -44,7 +44,7 @@
 
 /* MII mode defines */
 #define MII_MODE_ENABLE		0x0
-#define RGMII_MODE_ENABLE	0xA
+#define RGMII_MODE_ENABLE	0x3A
 
 /* GPIO that controls power to DDR on EVM-SK */
 #define GPIO_DDR_VTT_EN		7