powerpc/mpc85xx: implement workaround for errata DDR111 and DDR134

powerpc/mpc85xx: implement workaround for errata DDR111 and DDR134

Workaround for the following errata:
DDR111 - MCKE signal may not function correctly at assertion of HRESET
DDR134 - The automatic CAS-to-Preamble feature of the DDR controller can
         calibrate to incorrect values

These two workarounds must be implemented together because they touch
common registers.

Signed-off-by: York Sun <yorksun@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>