pinctrl: baytrail: Add missing spinlock usage in byt_gpio_irq_handler

pinctrl: baytrail: Add missing spinlock usage in byt_gpio_irq_handler

commit cdca06e4e85974d8a3503ab15709dbbaf90d3dd1 upstream.

According to VLI64 Intel Atom E3800 Specification Update (#329901)
concurrent read accesses may result in returning 0xffffffff and write
accesses may be dropped silently.
To workaround all accesses must be protected by locks.

Signed-off-by: Alexander Stein <alexander.stein@systec-electronic.com>
Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>