hw/qxl: fix -Werror=maybe-uninitialized false-positives

../hw/display/qxl.c:1352:5: error: ‘pci_region’ may be used uninitialized [-Werror=maybe-uninitialized]
../hw/display/qxl.c:1365:22: error: ‘pci_start’ may be used uninitialized [-Werror=maybe-uninitialized]

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>

hw/display/qxl.c

@@ -1301,8 +1301,8 @@ static int qxl_add_memslot(PCIQXLDevice *d, uint32_t slot_id, uint64_t delta,
     };
     uint64_t guest_start;
     uint64_t guest_end;
-    int pci_region;
-    pcibus_t pci_start;
+    int pci_region = -1;
+    pcibus_t pci_start = PCI_BAR_UNMAPPED;
     pcibus_t pci_end;
     MemoryRegion *mr;
     intptr_t virt_start;