iwlwifi: rs: split rs_collect_tx_data

Make _rs_collect_tx_data get window as param, in order
to be able to set various windows.

This will be used later for saving tpc statistics
as well.

Signed-off-by: Eliad Peller <eliadx.peller@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>