fsl-ddr: add the DDR3 SPD infrastructure

- support mirrored DIMMs, not support register DIMMs
- test passed on P2020DS board with MT9JSF12872AY-1G1D1
- test passed on MPC8569MDS board with MT8JSF12864HY-1G1D1

Signed-off-by: Dave Liu <daveliu@freescale.com>
Signed-off-by: Travis Wheatley <travis.wheatley@freescale.com>
diff --git a/cpu/mpc85xx/ddr-gen3.c b/cpu/mpc85xx/ddr-gen3.c
index 99c325a..8ac3d5f 100644
--- a/cpu/mpc85xx/ddr-gen3.c
+++ b/cpu/mpc85xx/ddr-gen3.c
@@ -98,10 +98,12 @@
 #endif
 
 	/*
-	 * 200 painful micro-seconds must elapse between
+	 * 500 painful micro-seconds must elapse between
 	 * the DDR clock setup and the DDR config enable.
+	 * DDR2 need 200 us, and DDR3 need 500 us from spec,
+	 * we choose the max, that is 500 us for all of case.
 	 */
-	udelay(200);
+	udelay(500);
 	asm volatile("sync;isync");
 
 	/* Let the controller go */