Print error when failing to load PCI config data

When loading migration fails due to a disagreement about
PCI config data we don't currently get any errors explaining
that was the cause of the problem or which byte in the config
data was at fault.
Signed-off-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: NMichael Tokarev <mjt@tls.msk.ru>

hw/pci/pci.c

@@ -428,6 +428,10 @@ static int get_pci_config_device(QEMUFile *f, void *pv, size_t size)
     for (i = 0; i < size; ++i) {
         if ((config[i] ^ s->config[i]) &
             s->cmask[i] & ~s->wmask[i] & ~s->w1cmask[i]) {
+            error_report("%s: Bad config data: i=0x%x read: %x device: %x "
+                         "cmask: %x wmask: %x w1cmask:%x", __func__,
+                         i, config[i], s->config[i],
+                         s->cmask[i], s->wmask[i], s->w1cmask[i]);
             g_free(config);
             return -EINVAL;
         }