MLK-17144 driver: soc: use mutex for power domain of imx8mq

MLK-17144 driver: soc: use mutex for power domain of imx8mq

In current gpc-psci.c file, the irqchip driver and gpc power
domain driver use the same spinlock to prevent concurrent
access to the GPC module. But actually, the irq and power domain
are two seperated function and controlled by different registers.

when using the same spinlock for these two funcition, in some corner
case the system will be deadlock if the spinlock is already acquired
by the power domain, but the power domain on/off is interrupted by
timer IRQ. So adding a mutex for power domain driver.

Signed-off-by: Bai Ping <ping.bai@nxp.com>
Reviewed-by: Anson Huang <Anson.Huang@nxp.com>