ARM: DRA7: EMIF: Update SDRAM_REF_CTRL register value

The value in SDRAM_REF_CTRL controls the delay time between
the initial rising edge of DDR_RESETn to rising edge of DDR_CKE
(JEDEC specs this as 500us). In order to achieve this, SDRAM_REF_CTRL
should be written with a value corresponding to 500us delay before
starting DDR initialization sequence, and configure proper
value at the end of sequence.

Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
diff --git a/board/ti/beagle_x15/board.c b/board/ti/beagle_x15/board.c
index db96e34..3a7e04d 100644
--- a/board/ti/beagle_x15/board.c
+++ b/board/ti/beagle_x15/board.c
@@ -47,7 +47,8 @@
 	.sdram_config_init	= 0x61851b32,
 	.sdram_config		= 0x61851b32,
 	.sdram_config2		= 0x00000000,
-	.ref_ctrl		= 0x00001035,
+	.ref_ctrl		= 0x000040F1,
+	.ref_ctrl_final		= 0x00001035,
 	.sdram_tim1		= 0xceef266b,
 	.sdram_tim2		= 0x328f7fda,
 	.sdram_tim3		= 0x027f88a8,
@@ -103,7 +104,8 @@
 	.sdram_config_init	= 0x61851b32,
 	.sdram_config		= 0x61851b32,
 	.sdram_config2		= 0x00000000,
-	.ref_ctrl		= 0x00001035,
+	.ref_ctrl		= 0x000040F1,
+	.ref_ctrl_final		= 0x00001035,
 	.sdram_tim1		= 0xceef266b,
 	.sdram_tim2		= 0x328f7fda,
 	.sdram_tim3		= 0x027f88a8,