iwlwifi: mvm: several fixes in scan

The firmware doesn't handle properly the fragmented scan.
Stop using it.
While at it change max_out_time and suspend_time units from
usec to TUs as expected by firmware API.

Signed-off-by: Alexander Bondar <alexander.bondar@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>