serial: sh-sci: Fix for port types without BRI interrupts.

In doing the evt2irq() + muxed vector conversion for various port types
it became apparent that some of the legacy port types will presently
error out due to the irq requesting logic attempting to acquire the
non-existent BRI IRQ. This adds some sanity checks to the request/free
path to ensure that non-existence of a source in itself is not an error.

This should restore functionality for legacy PORT_SCI ports.
Signed-off-by: NPaul Mundt <lethal@linux-sh.org>

drivers/tty/serial/sh-sci.c

@@ -1052,9 +1052,17 @@ static int sci_request_irq(struct sci_port *port)
 		if (SCIx_IRQ_IS_MUXED(port)) {
 			i = SCIx_MUX_IRQ;
 			irq = up->irq;
-		} else
+		} else {
 			irq = port->cfg->irqs[i];
 
+			/*
+			 * Certain port types won't support all of the
+			 * available interrupt sources.
+			 */
+			if (unlikely(!irq))
+				continue;
+		}
+
 		desc = sci_irq_desc + i;
 		port->irqstr[j] = kasprintf(GFP_KERNEL, "%s:%s",
 					    dev_name(up->dev), desc->desc);
@@ -1094,6 +1102,15 @@ static void sci_free_irq(struct sci_port *port)
 	 * IRQ first.
 	 */
 	for (i = 0; i < SCIx_NR_IRQS; i++) {
+		unsigned int irq = port->cfg->irqs[i];
+
+		/*
+		 * Certain port types won't support all of the available
+		 * interrupt sources.
+		 */
+		if (unlikely(!irq))
+			continue;
+
 		free_irq(port->cfg->irqs[i], port);
 		kfree(port->irqstr[i]);