drm/panfrost:fix the exception name always "UNKNOWN"

The exception_code in register is only 8 bits,So if
fault_status in panfrost_gpu_irq_handler() don't
(& 0xFF),it can't get correct exception reason.

and it's better to show all of the register value
to custom,so it's better fault_status don't (& 0xFF).
Signed-off-by: ChunyouTang <tangchunyou@icubecorp.cn>
Reviewed-by: Steven Price <steven.price@arm.com>
Signed-off-by: Steven Price <steven.price@arm.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210708073407.2015-1-tangchunyou@163.com

drivers/gpu/drm/panfrost/panfrost_gpu.c

@@ -33,7 +33,7 @@ static irqreturn_t panfrost_gpu_irq_handler(int irq, void *data)
 		address |= gpu_read(pfdev, GPU_FAULT_ADDRESS_LO);
 
 		dev_warn(pfdev->dev, "GPU Fault 0x%08x (%s) at 0x%016llx\n",
-			 fault_status & 0xFF, panfrost_exception_name(fault_status),
+			 fault_status, panfrost_exception_name(fault_status & 0xFF),
 			 address);
 
 		if (state & GPU_IRQ_MULTIPLE_FAULT)