Input: uinput - use monotonic times for timestamps

struct timeval which is part of struct input_event to maintain the event
times is not y2038 safe.

Real time timestamps are also not ideal for input_event as this time can go
backwards as noted in the patch a80b83b7

 by John Stultz.

The patch switches the timestamps to use monotonic time from realtime time.
This is assuming no one is using absolute times from these timestamps.

The structure to maintain input events will be changed in a different
patch.

Signed-off-by: Deepa Dinamani <deepa.kernel@gmail.com>
Acked-by: Peter Hutterer <peter.hutterer@who-t.net>
Patchwork-Id: 10118255
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>