ppc/85xx: Clean up use of LAWAR defines

On 85xx platforms we shouldn't be using any LAWAR_* defines
but using the LAW_* ones provided by fsl-law.h.  Rename any such
uses and limit the LAWAR_ to the 83xx platform as the only user so
we will get compile errors in the future.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>