[PATCH] irqchip: tb10x: use 'fallthrough' to eliminate a warning

[Randy Dunlap]

Use the 'fallthrough' macro to document that this switch case
does indeed fall through to the next case.

../drivers/irqchip/irq-tb10x.c: In function 'tb10x_irq_set_type':
../drivers/irqchip/irq-tb10x.c:62:13: warning: this statement may fall through [-Wimplicit-fallthrough=]
   62 |   flow_type = IRQ_TYPE_LEVEL_LOW;
../drivers/irqchip/irq-tb10x.c:63:2: note: here
   63 |  case IRQ_TYPE_LEVEL_LOW:
      |  ^~~~

Fixes: b06eb0173ef1 ("irqchip: Add TB10x interrupt controller driver")
Signed-off-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Marc Zyngier <maz@xxxxxxxxxx>
Cc: Christian Ruppert <christian.ruppert@xxxxxxxxxx>
---
 drivers/irqchip/irq-tb10x.c |    1 +
 1 file changed, 1 insertion(+)

--- linux-next-20210420.orig/drivers/irqchip/irq-tb10x.c
+++ linux-next-20210420/drivers/irqchip/irq-tb10x.c
@@ -60,6 +60,7 @@ static int tb10x_irq_set_type(struct irq
 		break;
 	case IRQ_TYPE_NONE:
 		flow_type = IRQ_TYPE_LEVEL_LOW;
+		fallthrough;
 	case IRQ_TYPE_LEVEL_LOW:
 		mod ^= im;
 		pol ^= im;