iwlwifi: mvm: move iwl_mvm_sta_alloc_queue() down

We want to call iwl_mvm_inactivity_check() from here in the
next patch, so need to move the code down to be able to.

Fix a minor checkpatch complaint while at it.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>