uboot-phytec

powerpc/mpc85xx: Add CONFIG_DDR_CLK_FREQ for corenet platform

New corenet platforms with chassis2 have separated DDR clock inputs. Use
CONFIG_DDR_CLK_FREQ for DDR clock. This patch also cleans up the logic of
detecting and displaying synchronous vs asynchronous mode.

Signed-off-by: York Sun <yorksun@freescale.com>
Signed-off-by: Andy Fleming <afleming@freescale.com>