[U-Boot] powerpc/mpc85xx: work around erratum A-006593

[Andy Fleming]

On Wed, May 15, 2013 at 05:50:13PM -0500, Scott Wood wrote:
> Erratum A-006593 is "Atomic store may report failure but still allow
> the store data to be visible".
> 
> The workaround is: "Set CoreNet Platform Cache register CPCHDBCR0 bit
> 21 to 1'b1.  This may have a small impact on synthetic write bandwidth
> benchmarks but should have a negligible impact on real code."
> 
> Signed-off-by: Scott Wood <scottwood at freescale.com>

Applied, thanks!

Andy