iwlwifi: mvm: fix possible memory leak

In case of invalid section_id, the function returns after
it aleready allocated memory. Fixed by change the order of actions.

Signed-off-by: Eytan Lifshitz <eytan.lifshitz@intel.com>
Reviewed-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>