Better factor the ppc hash translation path

Better factor the ppc hash translation path

Currently the path handling hash page table translation in get_segment()
has a mix of common and 32 or 64 bit specific code.  However the
division is not done terribly well which results in a lot of messy code
flipping between common and divided paths.

This patch improves the organization, consolidating several divided paths
into one.  This in turn allows simplification of some code in
get_segment(), removing a number of ugly interim variables.

This new factorization will also make it easier to add support for the 1T
segments added in newer CPUs.

Signed-off-by: David Gibson <dwg@au1.ibm.com>
Signed-off-by: Alexander Graf <agraf@suse.de>