iwlwifi: mvm: remove deprecated scan API code

The legacy scan API is deprecated and not used anymore with 10 and
higher firmware versions.  Since we deprecated firmware version 9, we
can remove a whole lot of unused code.

Signed-off-by: Luciano Coelho <luciano.coelho@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>