iwlwifi: mvm: differentiate net-detect from sched scan

Net-detect scans were using the same type as sched scan, which was
causing the driver to return -EBUSY and prevent the system from
suspending if there was an ongoing scheduled scan.  To avoid this, add
a new type for net-detect and don't stop anything when it is
requested, so that the existing scheduled scan will be resumed when
the system wakes up.

Signed-off-by: Luciano Coelho <luciano.coelho@intel.com>
Reviewed-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>