platform/x86: intel_int0002_vgpio: Use acpi_register_wakeup_handler()

The Power Management Events (PMEs) the INT0002 driver listens for get
signalled by the Power Management Controller (PMC) using the same IRQ
as used for the ACPI SCI.

Since commit fdde0ff8 ("ACPI: PM: s2idle: Prevent spurious SCIs from
waking up the system") the SCI triggering, without there being a wakeup
cause recognized by the ACPI sleep code, will no longer wakeup the system.

This breaks PMEs / wakeups signalled to the INT0002 driver, the system
never leaves the s2idle_loop() now.

Use acpi_register_wakeup_handler() to register a function which checks
the GPE0a_STS register for a PME and trigger a wakeup when a PME has
been signalled.

Fixes: fdde0ff8 ("ACPI: PM: s2idle: Prevent spurious SCIs from waking up the system")
Cc: 5.4+ <stable@vger.kernel.org> # 5.4+
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>