Implement wifi_qsap_set_tx_power

Used by radio proprietary binaries from Motorola.

Change-Id: I9fd49cbba6001a4c7ddadf5cb88df06d6146f01a

softap/sdk/qsap.h

@@ -52,6 +52,8 @@ s32 wifi_qsap_start_softap_in_concurrency(void);
 s32 wifi_qsap_stop_softap_in_concurrency(void);
 #endif
 
+s32 wifi_qsap_set_tx_power(s32);
+
 #if __cplusplus
 };  // extern "C"
 #endif