driver/ddr: Change Freescale ARM DDR driver to support both big and little endian

Initially it was believed the DDR controller on Freescale ARM would have
big endian. But some platform will have little endian.

Signed-off-by: York Sun <yorksun@freescale.com>
diff --git a/README b/README
index 6668631..413d682 100644
--- a/README
+++ b/README
@@ -486,6 +486,12 @@
 		PBI commands can be used to configure SoC before it starts the execution.
 		Please refer doc/README.pblimage for more details
 
+		CONFIG_SYS_FSL_DDR_BE
+		Defines the DDR controller register space as Big Endian
+
+		CONFIG_SYS_FSL_DDR_LE
+		Defines the DDR controller register space as Little Endian
+
 - Intel Monahans options:
 		CONFIG_SYS_MONAHANS_RUN_MODE_OSC_RATIO