gpio: aspeed-sgpio: Convert aspeed_sgpio.lock to raw_spinlock

The gpio-aspeed-sgpio driver implements an irq_chip which need to be
invoked from hardirq context. Since spin_lock() can sleep with
PREEMPT_RT, it is no longer legal to invoke it while interrupts are
disabled.
This also causes lockdep to complain about:
[   25.919465] [ BUG: Invalid wait context ]
because aspeed_sgpio.lock (spin_lock_t) is taken under irq_desc.lock
(raw_spinlock_t).
Let's use of raw_spinlock_t instead of spinlock_t.

Signed-off-by: Iwona Winiarska <iwona.winiarska@intel.com>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>