mailbox: zynqmp: Fix IPI isr handling

Multiple IPI channels are mapped to same interrupt handler.
Current isr implementation handles only one channel per isr.
Fix this behavior by checking isr status bit of all child
mailbox nodes.

Fixes: 4981b82ba2ff ("mailbox: ZynqMP IPI mailbox controller")
Signed-off-by: Tanmay Shah <[e-mail]>
Acked-by: Michal Simek <[e-mail]>
Cc: [e-mail]
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Mathieu Poirier <[e-mail]>

drivers/mailbox/zynqmp-ipi-mailbox.c

···
 	struct zynqmp_ipi_message *msg;
 	u64 arg0, arg3;
 	struct arm_smccc_res res;
-	int ret, i;
+	int ret, i, status = IRQ_NONE;
 
 	(void)irq;
 	arg0 = SMC_IPI_MAILBOX_STATUS_ENQUIRY;
···
 				memcpy_fromio(msg->data, mchan->req_buf,
 					      msg->len);
 				mbox_chan_received_data(chan, (void *)msg);
-				return IRQ_HANDLED;
+				status = IRQ_HANDLED;
 			}
 		}
 	}
-	return IRQ_NONE;
+	return status;
 }
 
 /**