target-ppc: Fix htab_mask calculation

target-ppc: Fix htab_mask calculation

Correctly update the htab_mask using the return value of
KVM_PPC_ALLOCATE_HTAB ioctl. Also we don't update sdr1
on GET_SREGS for HV. We check for external htab and if
found true, we don't need to update sdr1

Signed-off-by: Aneesh Kumar K.V <[email protected]>
[ fixed pte group offset computation in ppc_hash64_htab_lookup() that
  caused TCG to fail, Greg Kurz <[email protected]> ]
Signed-off-by: Greg Kurz <[email protected]>
Signed-off-by: Alexander Graf <[email protected]>