Ignore TX interrupts when there are not packets buffered. This fix a problem seen with realtek 80[12]9 based cards; noted by scomeau@obscurity.org.
Ignore TX interrupts when there are not packets buffered.
This fix a problem seen with realtek 80[12]9 based cards; noted by
scomeau@obscurity.org.

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