e500: fix memory leak

Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Stefan Weil <sw@weilnetz.de>

hw/ppc/e500.c

@@ -308,6 +308,7 @@ static int ppce500_load_device_tree(MachineState *machine,
         }
 
         fdt = load_device_tree(filename, &fdt_size);
+        g_free(filename);
         if (!fdt) {
             goto out;
         }