qemuNodeDeviceDetachFlags: Avoid use of uninitialized variables

After abf75aea the compiler screams:

qemu/qemu_driver.c: In function 'qemuNodeDeviceDetachFlags':
qemu/qemu_driver.c:10693:9: error: 'domain' may be used uninitialized in this function [-Werror=maybe-uninitialized]
     pci = virPCIDeviceNew(domain, bus, slot, function);
         ^
qemu/qemu_driver.c:10693:9: error: 'bus' may be used uninitialized in this function [-Werror=maybe-uninitialized]
qemu/qemu_driver.c:10693:9: error: 'slot' may be used uninitialized in this function [-Werror=maybe-uninitialized]
qemu/qemu_driver.c:10693:9: error: 'function' may be used uninitialized in this function [-Werror=maybe-uninitialized]

Since the other functions qemuNodeDeviceReAttach and qemuNodeDeviceReset
looks exactly the same, I've initialized the variables there as well.
However, I am still wondering why those functions don't matter to gcc
while the first one does.

src/qemu/qemu_driver.c

@@ -10669,7 +10669,7 @@ qemuNodeDeviceDetachFlags(virNodeDevicePtr dev,
 {
     virQEMUDriverPtr driver = dev->conn->privateData;
     virPCIDevicePtr pci = NULL;
-    unsigned domain, bus, slot, function;
+    unsigned domain = 0, bus = 0, slot = 0, function = 0;
     int ret = -1;
     virNodeDeviceDefPtr def = NULL;
     char *xml = NULL;
@@ -10737,7 +10737,7 @@ qemuNodeDeviceReAttach(virNodeDevicePtr dev)
     virQEMUDriverPtr driver = dev->conn->privateData;
     virPCIDevicePtr pci = NULL;
     virPCIDevicePtr other;
-    unsigned domain, bus, slot, function;
+    unsigned domain = 0, bus = 0, slot = 0, function = 0;
     int ret = -1;
     virNodeDeviceDefPtr def = NULL;
     char *xml = NULL;
@@ -10799,7 +10799,7 @@ qemuNodeDeviceReset(virNodeDevicePtr dev)
 {
     virQEMUDriverPtr driver = dev->conn->privateData;
     virPCIDevicePtr pci;
-    unsigned domain, bus, slot, function;
+    unsigned domain = 0, bus = 0, slot = 0, function = 0;
     int ret = -1;
     virNodeDeviceDefPtr def = NULL;
     char *xml = NULL;