in txp_intr() only refill the rx buffer ring if it is empty; based on suggestion from Pankaj Chhabra.
in txp_intr() only refill the rx buffer ring if it is empty; based on
suggestion from Pankaj Chhabra.

orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars