MLK-15009 irqchip: imx-irqsteer: correct type of irqstat

MLK-15009 irqchip: imx-irqsteer: correct type of irqstat

The type of irqstat in irqsteer_irqchip_data unsigned long, actually
it needs to be 32bits width, so use unsigned int.

And use sizeof(irqsteer_data->irqstat[0]), instead of 4 when alloc
memory for irqsteer_data.

for_each_set_bit needs the second param type is unsigned long *, so
cast the irqsteer_data->irqstat to unsigned long *, this is safe here.

Signed-off-by: Peng Fan <peng.fan@nxp.com>