wl12xx: fix sched scan of DFS channels

DFS channels weren't scanned properly because
min/max_duration weren't set for these channels
even though they're required by the FW.
The change sets passive_duration and min/max_duration
for all channels as the FW uses the correct parameters
according to the channel type.

Signed-off-by: Eyal Shapira <eyal@wizery.com>
Signed-off-by: Luciano Coelho <coelho@ti.com>