libxl: Fix if{} nesting in do_pci_remove

do_pci_remove contained this:

    if (type == LIBXL_DOMAIN_TYPE_HVM) {
       [stuff]
    } else if (type != LIBXL_DOMAIN_TYPE_PV)
        abort();
    {

This is bizarre, and not correct.  The effect is that HVM guests end
up running both the proper code and that intended for PV guests.  This
causes (amongst other things) trouble when PCI devices are
hot-unplugged from HVM guests.

This bug was introduced in abfb006f "tools/libxl: explicitly grant
access to needed I/O-memory ranges".

This is clear candidate for Xen 4.5, being a bugfix to an important
feature.

Reported-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
Tested-by: Robert Hu <robert.hu@intel.com>
Rlease-Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
CC: Sander Eikelenboom <linux@eikelenboom.it>
CC: George Dunlap <George.Dunlap@eu.citrix.com>

tools/libxl/libxl_pci.c

@@ -1247,9 +1247,9 @@ static int do_pci_remove(libxl__gc *gc, uint32_t domid,
             rc = ERROR_FAIL;
             goto out_fail;
         }
-    } else if (type != LIBXL_DOMAIN_TYPE_PV)
-        abort();
-    {
+    } else {
+        assert(type == LIBXL_DOMAIN_TYPE_PV);
+
         char *sysfs_path = libxl__sprintf(gc, SYSFS_PCI_DEV"/"PCI_BDF"/resource", pcidev->domain,
                                          pcidev->bus, pcidev->dev, pcidev->func);
         FILE *f = fopen(sysfs_path, "r");