PCI: pciehp: Avoid implicit fallthroughs in switch statements

Per Mika's request, add an explicit break to the last case of switch
statements everywhere in pciehp to be more defensive towards future
amendments.

Per Gustavo's request, mark all non-empty implicit fallthroughs with a
comment to silence warnings triggered by -Wimplicit-fallthrough=2.

Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Acked-by: Gustavo A. R. Silva <gustavo@embeddedor.com>

drivers/pci/hotplug/pciehp_ctrl.c

@@ -211,6 +211,7 @@ void pciehp_handle_disable_request(struct slot *slot)
 	case BLINKINGON_STATE:
 	case BLINKINGOFF_STATE:
 		cancel_delayed_work(&slot->work);
+		break;
 	}
 	slot->state = POWEROFF_STATE;
 	mutex_unlock(&slot->lock);
@@ -232,6 +233,7 @@ void pciehp_handle_presence_or_link_change(struct slot *slot, u32 events)
 	switch (slot->state) {
 	case BLINKINGOFF_STATE:
 		cancel_delayed_work(&slot->work);
+		/* fall through */
 	case ON_STATE:
 		slot->state = POWEROFF_STATE;
 		mutex_unlock(&slot->lock);
@@ -245,6 +247,7 @@ void pciehp_handle_presence_or_link_change(struct slot *slot, u32 events)
 		break;
 	default:
 		mutex_unlock(&slot->lock);
+		break;
 	}
 
 	/* Turn the slot on if it's occupied or link is up */
@@ -259,6 +262,7 @@ void pciehp_handle_presence_or_link_change(struct slot *slot, u32 events)
 	switch (slot->state) {
 	case BLINKINGON_STATE:
 		cancel_delayed_work(&slot->work);
+		/* fall through */
 	case OFF_STATE:
 		slot->state = POWERON_STATE;
 		mutex_unlock(&slot->lock);
@@ -272,6 +276,7 @@ void pciehp_handle_presence_or_link_change(struct slot *slot, u32 events)
 		break;
 	default:
 		mutex_unlock(&slot->lock);
+		break;
 	}
 }