During system suspend mark ACPI buttons (other than the lid) as
"suspended" and if in that state, report wakeup events on button
events, but do not propagate those events up the stack.

This prevents systems from being turned off after a button-triggered
wakeup from the "freeze" sleep state.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=77611
Tested-on: Acer Aspire S5, Toshiba Portege R500
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>