KVM: PPC: Remove fetch fail code

When instruction fetch failed, the inline function hook automatically
detects that and starts the internal guest memory load function. So
whenever we access kvmppc_get_last_inst(), we're sure the result is sane.

Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>