Only call bus_dmamap_unload() if we loaded a dmamap beforehand. Found out the hard way on sparc64. Now acx(4) no longer panics but it does not yet work.  OK mglocker@
Only call bus_dmamap_unload() if we loaded a dmamap beforehand. Found out
the hard way on sparc64. Now acx(4) no longer panics but it does not yet
work.  OK mglocker@

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