ACPI: PM: s2idle: Always set up EC GPE for system wakeup

Commit 10a08fd6 ("ACPI: PM: Set up EC GPE for system wakeup from
drivers that need it") assumed that the EC GPE would only need to be
set up for system wakeup if either the intel-hid or the intel-vbtn
driver was in use, but that turns out to be incorrect.  In particular,
on ASUS Zenbook UX430UNR/i7-8550U, if the EC GPE is not enabled while
suspended, the system cannot be woken up by opening the lid or
pressing a key, and that machine doesn't use any of the drivers
mentioned above.

For this reason, always set up the EC GPE for system wakeup from
suspend-to-idle by setting and clearing its wake mask in the ACPI
suspend-to-idle callbacks.

Fixes: 10a08fd6 ("ACPI: PM: Set up EC GPE for system wakeup from drivers that need it")
Reported-by: Kristian Klausen <kristian@klausen.dk>
Tested-by: Kristian Klausen <kristian@klausen.dk>
Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>