qcacmn: Filter out the 6ghz chan freq from valid freq list

Currently the driver does not have a support to
filter out the 6ghz frequencies from the valid freq
list, and hence there is a high chance of selecting
the 6ghz freq as an operating freq for SAP, which
the legacy clients won't be able to scan.

Fix is to add a support for filtering out the 6ghz
frequencies from the valid freq list.

Change-Id: I8e3552a254e2b79cc1fc09da3e1e06ac378cbb07
CRs-Fixed: 2801414

umac/dfs/dispatcher/inc/wlan_dfs_ioctl.h

@@ -211,6 +211,9 @@ struct dfs_bangradar_params {
 #define DFS_RANDOM_CH_FLAG_RESTRICTED_80P80_ENABLED 0x0200
 						       /* 0000 0010 0000 0000 */
 
+/* Flag to exclude all 6GHz channels */
+#define DFS_RANDOM_CH_FLAG_NO_6GHZ_CH          0x00400 /* 0000 0100 0000 0000 */
+
 /**
  * struct wlan_dfs_caps - DFS capability structure.
  * @wlan_dfs_ext_chan_ok:         Can radar be detected on the extension chan?