powerpc/85xx: Add nor flash partitions for mpc8569mds

Add 4 partitions in nor flash. Also fix nor flash bank width bug. The
flash is capable of x8/x16 width but is configured for x8.

Signed-off-by: Kevin Hao <kexin.hao@windriver.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>