PCI: keystone: Use ERR_IRQ_STATUS instead of ERR_IRQ_STATUS_RAW to get interrupt status

Use ERR_IRQ_STATUS instead of ERR_IRQ_STATUS_RAW to get interrupt
status. ERR_IRQ_STATUS_RAW has the status of the interrupts
before masking whereas ERR_IRQ_STATUS has the status of the interrupts
after masking. Since all the interrupts are unmasked here, use
ERR_IRQ_STATUS.

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>