package/xen: fix build with 64 bits time_t

Fix build of xen with 64 bites time_t:

/tmp/instance-0/output-1/build/xen-4.14.2/tools/qemu-xen/hw/input/virtio-input-host.c: In function 'virtio_input_host_handle_status':
/tmp/instance-0/output-1/build/xen-4.14.2/tools/qemu-xen/hw/input/virtio-input-host.c:198:28: error: 'struct input_event' has no member named 'time'
  198 |     if (gettimeofday(&evdev.time, NULL)) {
      |                            ^

Fixes:
 - http://autobuild.buildroot.org/results/136ce42f44bf48d3db4eda7b1548bf7ac1b97d51



Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>