iwlwifi: mvm: rs: don't use shadowing variable

The variable 'tid' is already defined in this function, so use
just 't' for the new one. As we return from the function just
overwriting 'tid' would be acceptable, but less obvious to the
reader.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>