qcacld-3.0: Add fallthrough comment in __iw_set_host_offload()

In __iw_set_host_offload() there is a switch statement where the logic
for case WLAN_OFFLOAD_ARP_AND_BC_FILTER_ENABLE falls through to the
next case. Add a fallthrough comment to explicitly document that this
is the desired behavior as opposed to a missing break statement.

Change-Id: I9a7d84841d9d059e822ee15ee482111ca9d87caf
CRs-Fixed: 2233178

core/hdd/src/wlan_hdd_wext.c

@@ -8054,6 +8054,7 @@ static int __iw_set_host_offload(struct net_device *dev,
 			break;
 		case WLAN_OFFLOAD_ARP_AND_BC_FILTER_ENABLE:
 			hdd_debug("   BC Filtering enable");
+			/* fallthrough */
 		case WLAN_OFFLOAD_ENABLE:
 			hdd_debug("   ARP offload enable");
 			hdd_debug("   IP address: %d.%d.%d.%d",