Input: evdev - add CLOCK_BOOTTIME support

This patch adds support for CLOCK_BOOTTIME for input event timestamp.
CLOCK_BOOTTIME includes suspend time, so it would allow aplications
to get correct time difference between two events even when system
resumes from suspend state.

Signed-off-by: Aniroop Mathur <a.mathur@samsung.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>