KVM: MMU: remove KVM host pv mmu support

The host side pv mmu support has been marked for feature removal in
January 2011.  It's not in use, is slower than shadow or hardware
assisted paging, and a maintenance burden.  It's November 2011, time to
remove it.

Signed-off-by: Chris Wright <chrisw@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>