pinctrl: rockchip: convert to raw spinlock

This lock is used from rockchip_irq_set_type() which is part of the
irq_chip implementation and thus must use raw_spinlock_t as documented
in Documentation/gpio/driver.txt.

Signed-off-by: John Keeping <john@metanate.com>
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>