powerpc/mpc8xxx: Add 16-bit support for DDR3

Add support for 16-bit DDR bus. Also deal with system using 64- and 32-bit
DDR devices.

Signed-off-by: York Sun <yorksun@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
diff --git a/arch/powerpc/include/asm/fsl_ddr_sdram.h b/arch/powerpc/include/asm/fsl_ddr_sdram.h
index 127a840..1778cc5 100644
--- a/arch/powerpc/include/asm/fsl_ddr_sdram.h
+++ b/arch/powerpc/include/asm/fsl_ddr_sdram.h
@@ -181,6 +181,9 @@
 	unsigned int all_DIMMs_minimum_tRCD_ps;
 } memctl_options_partial_t;
 
+#define DDR_DATA_BUS_WIDTH_64 0
+#define DDR_DATA_BUS_WIDTH_32 1
+#define DDR_DATA_BUS_WIDTH_16 2
 /*
  * Generalized parameters for memory controller configuration,
  * might be a little specific to the FSL memory controller