KVM: PPC: Book3S HV: Don't use ASDR for real-mode HPT faults on POWER9

KVM: PPC: Book3S HV: Don't use ASDR for real-mode HPT faults on POWER9

In HPT mode on POWER9, the ASDR register is supposed to record
segment information for hypervisor page faults.  It turns out that
POWER9 DD1 does not record the page size information in the ASDR
for faults in guest real mode.  We have the necessary information
in memory already, so by moving the checks for real mode that already
existed, we can use the in-memory copy.  Since a load is likely to
be faster than reading an SPR, we do this unconditionally (not just
for POWER9 DD1).

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>