iommu/vt-d: Fix NULL pointer dereference in prq_event_thread()

When handling page request without pasid event, go to "no_pasid"
branch instead of "bad_req". Otherwise, a NULL pointer deference
will happen there.

Cc: Ashok Raj <ashok.raj@intel.com>
Cc: Jacob Pan <jacob.jun.pan@linux.intel.com>
Cc: Sohil Mehta <sohil.mehta@intel.com>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Fixes: a222a7f0 'iommu/vt-d: Implement page request handling'
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/intel-svm.c

@@ -595,7 +595,7 @@ static irqreturn_t prq_event_thread(int irq, void *d)
 			pr_err("%s: Page request without PASID: %08llx %08llx\n",
 			       iommu->name, ((unsigned long long *)req)[0],
 			       ((unsigned long long *)req)[1]);
-			goto bad_req;
+			goto no_pasid;
 		}
 
 		if (!svm || svm->pasid != req->pasid) {