85xx: Handle eLBC difference w/36-bit physical

The eLBC only handles 32-bit physical address in systems with 36-bit
physical.  The previos generation of LBC handled 34-bit physical
address in 36-bit systems.  Added a new CONFIG option to convey
the difference between the LBC and eLBC.

Also added defines for XAM bits used in LBC for the extended 34-bit
support.

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