gpio / ACPI: Use local variable instead of ACPI_HANDLE()

In acpi_gpiochip_request_interrupts() the handle local
variable already contains the value that we want to pass
to acpi_walk_resources(), so it is better to use that
variable instead of evaluating ACPI_HANDLE() once more
for the same device.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>