[wlan][sme] Exclude DFS channels in active scan

Exclude dFS channels in active scan request if device does not handle
such channels properly.

Test:
1. runtests /pkgfs/packages/wlan-sme-tests/0/test
2. Verify all channels included for passive scan.
3. Verify DFS channel excluded on ralink and ath10k for active scan. All
   channels are included on broadcom.

Change-Id: Ib8d4c5e64204509294a0e1bf3357868b295cf97d