KVM: PPC: Book3S HV: Put huge-page HPTEs in rmap chain for base address

Currently, when a huge page is faulted in for a guest, we select the
rmap chain to insert the HPTE into based on the guest physical address
that the guest tried to access.  Since there is an rmap chain for each
system page, there are many rmap chains for the area covered by a huge
page (e.g. 256 for 16MB pages when PAGE_SIZE = 64kB), and the huge-page
HPTE could end up in any one of them.

For consistency, and to make the huge-page HPTEs easier to find, we now
put huge-page HPTEs in the rmap chain corresponding to the base address
of the huge page.

Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>