fsl_ddr_get_dimm_params() should be wrapped by
CONFIG_SYS_DDR_RAW_TIMING, otherwise, when using fixed_sdram() instead of
using SPD, it will cause compile error.
Signed-off-by: Shaohui Xie <Shaohui.Xie@freescale.com> Acked-by: York Sun <yorksun@freescale.com> Signed-off-by: Andy Fleming <afleming@freescale.com>