cnss: Add Set/Get DFS NOL APIs

According to 802.11h spec, once the radar detection is done, AP
shouldn't try to use the No Occupancy List (NOL). Since WLAN
driver is a module, there is no way for WLAN driver to store the
DFS NOL info. So adding Set and Get APIs so that DFS NOL info is
stored in CNSS driver before unloading WLAN driver and info is
queried back once the driver is brought-up again.

CRs-fixed: 661350
Change-Id: I9b99df7c351a45593a3febbbdda731771475b6d4
Signed-off-by: Prashanth Bhatta <bhattap@codeaurora.org>