x86: Fix pirq teardown on domain destruction.

The privilege check in unmap_domain_pirq() fails since the teardown
completes in RCU (idle domain) context. We can remove the check since
it is covered in physdev_op() already, which is the only potentially
unprivileged caller.

Signed-off-by: Wei Gang <gang.wei@intel.com>

xen/arch/x86/irq.c

@@ -1567,9 +1567,6 @@ int unmap_domain_pirq(struct domain *d, int pirq)
     if ( (pirq < 0) || (pirq >= d->nr_pirqs) )
         return -EINVAL;
 
-    if ( !IS_PRIV_FOR(current->domain, d) )
-        return -EINVAL;
-
     ASSERT(spin_is_locked(&pcidevs_lock));
     ASSERT(spin_is_locked(&d->event_lock));