wl12xx: fix forced passive scans

We were using incorrect max and min dwell times during forced passive
scans because we were still using the active scan states to scan
(passively) the channels that were not marked as passive.

Instead of doing passive scans in active states, we now skip active
states and scan for all channels in passive states.

Cc: <stable@kernel.org> # 2.6.36+
Signed-off-by: Luciano Coelho <coelho@ti.com>