ACPI: button: trigger wakeup key events

Andorid can wakeup from various wakeup sources, but only several wakeup
sources can wake up screen with right events(POWER, WAKEUP) from input
device.

Regarding pressing acpi power button, it can resume system and
ACPI_BITMASK_WAKE_STATUS and ACPI_BITMASK_POWER_BUTTON_STATUS are set in
pm1a_sts, but kernel does not report any key event to user space during
resuming by default.

So, send wakeup key event to user space during resume from power button.

Signed-off-by: Ken Xue <Ken.Xue@amd.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
[ rjw: Subject edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>