Reserved for ACPI actually means that in such case the GPIO hardware will
not update the interrupt status register (GPI_IS) even if the pin is
configured to trigger an interrupt. It will update GPI_GPE_STS instead and
does not trigger an interrupt.

Allow using such pins as GPIOs, only prevent their usage as interrupts.

We also rename function intel_pad_reserved_for_acpi() to be
intel_pad_acpi_mode() which reflects the actual meaning better.
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>