KVM: PPC: Book3s PR: Disable AIL mode with OPAL

When we're using PR KVM we must not allow the CPU to take interrupts
in virtual mode, as the SLB does not contain host kernel mappings
when running inside the guest context.

To make sure we get good performance for non-KVM tasks but still
properly functioning PR KVM, let's just disable AIL whenever a vcpu
is scheduled in.

This patch fixes running PR KVM on POWER8 bare metal for me.

Signed-off-by: Alexander Graf <agraf@suse.de>
KVM: PPC: Book3s HV: Fix tlbie compile error

Some compilers complain about uninitialized variables in the compute_tlbie_rb
function. When you follow the code path you'll realize that we'll never get
to that point, but the compiler isn't all that smart.

So just default to 4k page sizes for everything, making the compiler happy
and the code slightly easier to read.

Signed-off-by: Alexander Graf <agraf@suse.de>