ppc: fix hrfid, tlbia and slbia privilege

commit 74693da98894 ('ppc: tlbie, tlbia and tlbisync are HV only')
introduced some extra checks on the instruction privilege. slbia was
changed wrongly and hrfid, tlbia were forgotten.

Signed-off-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
