intel-vbtn: new driver for Intel Virtual Button

intel-vbtn: new driver for Intel Virtual Button

BugLink: https://bugs.launchpad.net/bugs/1609204
This driver supports power button event in Intel Virtual Button currently.
New Dell XPS 13 requires this driver for the power button.

This driver is copied/modified from intel-hid.c
Most credit goes to the author of intel-hid.c,
Alex Hung <alex.hung@canonical.com>

Signed-off-by: AceLan Kao <acelan.kao@canonical.com>
Signed-off-by: Darren Hart <dvhart@linux.intel.com>
(cherry picked from commit 332e081225fc2a657aa587c42943d5f5a7dae88b)
Signed-off-by: AceLan Kao <acelan.kao@canonical.com>
Acked-by: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>