wifi(implementation): Turn on DFS flag for STA

DFS flag needs to be turned on in the legacy HAL for STA operations. So,
initialize this flag on creation of STA iface.
PS: Not adding an explicit HIDL API for this since there is no need to
toggle this from framework and since the HIDL API's are frozen now.

Bug: 36169790
Test: Verified the fix with regression tests: b/37528903.
Change-Id: I214097fcb399cef7fc0cbd2c278622fac259a3e3
diff --git a/wifi/1.0/default/wifi_legacy_hal.h b/wifi/1.0/default/wifi_legacy_hal.h
index 576dfe6..1656f68 100644
--- a/wifi/1.0/default/wifi_legacy_hal.h
+++ b/wifi/1.0/default/wifi_legacy_hal.h
@@ -181,6 +181,7 @@
   wifi_error stopGscan(wifi_request_id id);
   std::pair<wifi_error, std::vector<uint32_t>> getValidFrequenciesForBand(
       wifi_band band);
+  wifi_error setDfsFlag(bool dfs_on);
   // Link layer stats functions.
   wifi_error enableLinkLayerStats(bool debug);
   wifi_error disableLinkLayerStats();