mainboard/google/parrot: fix ACPI interrupt storm on lid switch change

This fixes the ACPI interrupt storm on Parrot that happens when
closing the lid or entering suspend by lid close (seen in
/sys/firmware/acpi/interrupts/gpe1F). This patch inverts the interrupt
trigger level every time the interrupt is received so that it doesn't fire
until the next state change.  http://askubuntu.com/questions/310196
is a good example of what this is trying to solve.

Change-Id: I8b095914e9330c3217a4ceb058613fa952f4a234
Signed-off-by: Andrew Litt <ajlitt@splunge.net>
Reviewed-on: http://review.coreboot.org/6858
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Aaron Durbin <adurbin@google.com>