qcacmn: Fix compilation issue on arch32 by gcc 9.3

This change fixed compilation error about implicit-fallthrough and
pointer to in cast.

Change-Id: Iea2c25d97d8a039ed0f8083078427a8f8de70cd1
CRs-Fixed: 2814658

umac/scan/core/src/wlan_scan_manager_6ghz.c

@@ -271,7 +271,7 @@ scm_copy_valid_channels(struct wlan_objmgr_psoc *psoc,
 		 * Consider the complete channel list if firmware supports
 		 * RNR_ONLY scan flag/feature.
 		 */
-
+		/* fallthrough */
 	default:
 		/*
 		 * Allow all 2g/5g/6g channels. Below are also covered in this