iwlwifi: mvm: add extended dwell time

When doing active scan on crowded channels we are likely to miss probe
responses due to collisions. To overcome this issue we use an extended
dwell time on channels 1, 6 and 11; this dwell time is set to 100.

In case of fragmented scan extended dwell time is the maximum out of
channel time - 44 msec. Fragmented active scan will be addressed later.

Extended dwell time isn't used in sched scan or p2p find.

Signed-off-by: David Spinadel <david.spinadel@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>