Xen PCI passthrough: fix passthrough failure when no interrupt pin

Commit 5a11d0f mistakenly converted a log message into an error
condition when no pin interrupt is found for the pci device being
passed through. Revert that part of the commit.

Signed-off-by: Bruce Rogers <brogers@suse.com>
Signed-off-by: Stefano Stabellini <sstabellini@kernel.org>
Acked-by: Anthony PERARD <anthony.perard@citrix.com>
(cherry picked from commit 0968c91)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

hw/xen/xen_pt.c

@@ -842,7 +842,7 @@ static void xen_pt_realize(PCIDevice *d, Error **errp)
         goto err_out;
     }
     if (!scratch) {
-        error_setg(errp, "no pin interrupt");
+        XEN_PT_LOG(d, "no pin interrupt\n");
         goto out;
     }