[WCNCR00152848] softap: change dfs master shut down flow and dfs flag

[Description]
Change dfs master shut down flow and dfs flag
1. Add the timer to shut down dfs master
2. Change DFS master compile flag value
3. Enable DFS master by default with kernel version 3.13 or more recent

Change-Id: If68ff820eec2e92de57bfcba60db86819e776a35
Signed-off-by: Chun Lee <chun.lee@mediatek.com>
CR-Id: WCNCR00152848
Feature: softap
7 files changed