mmu-hash*: Add header file for definitions

mmu-hash*: Add header file for definitions

Currently cpu.h contains a number of definitions relating to the 64-bit
hash MMU.  Some are used in the MMU emulation code, but some are only used
in the spapr MMU management hcall implementations.

This patch moves these definitions (except for a few that are needed
more widely) into mmu-hash64.h header, shared between the MMU emulation
code and the spapr hcall code.  The MMU emulation code is also updated to
actually use a number of those definitions in place of hard coded
constants.

Similarly, we add new analogous definitions to mmu-hash32.h and use those
in place of many hard-coded constants in mmu-hash32.c

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
[agraf: fix 32-bit hosts]
Signed-off-by: Alexander Graf <agraf@suse.de>