[PATCH] genirq: Mark expected switch fall-through

["Gustavo A. R. Silva" <gustavo@embeddedor.com>]

In preparation to enabling -Wimplicit-fallthrough, mark switch
cases where we are expecting to fall through.

This patch fixes the following warning:

kernel/irq/manage.c: In function ‘irq_do_set_affinity’:
kernel/irq/manage.c:198:3: warning: this statement may fall through [-Wimplicit-fallthrough=]
   cpumask_copy(desc->irq_common_data.affinity, mask);
   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
kernel/irq/manage.c:199:2: note: here
  case IRQ_SET_MASK_OK_NOCOPY:
  ^~~~

In order to get the warning mentioned above, the following
line was added to the top Makefile:

KBUILD_CFLAGS  += $(call cc-option,-Wimplicit-fallthrough=3,)

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
---
 kernel/irq/manage.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 9ec34a2a6638..1401afa0d58a 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -196,6 +196,7 @@ int irq_do_set_affinity(struct irq_data *data, const struct cpumask *mask,
 	case IRQ_SET_MASK_OK:
 	case IRQ_SET_MASK_OK_DONE:
 		cpumask_copy(desc->irq_common_data.affinity, mask);
+		/* fall through */
 	case IRQ_SET_MASK_OK_NOCOPY:
 		irq_validate_effective_affinity(data);
 		irq_set_thread_affinity(desc);
-- 
2.21.0