vircgroupv2devices: Fix format string for size_t variable

In virCgroupV2DevicesReallocMap() we are debug printing both
arguments passed to the function. However, the @size argument is
type of size_t but '%lu' is used to format it.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>

src/util/vircgroupv2devices.c

@@ -456,7 +456,7 @@ virCgroupV2DevicesReallocMap(int mapfd,
     int ret = -1;
     VIR_AUTOCLOSE newmapfd = virCgroupV2DevicesCreateMap(size);
 
-    VIR_DEBUG("realloc devices map mapfd:%d, size:%lu", mapfd, size);
+    VIR_DEBUG("realloc devices map mapfd:%d, size:%zu", mapfd, size);
 
     if (newmapfd < 0)
         return -1;