On Octane, force a nonzero _dma_mask value so that we do not risk trying to handle a mapping partly in, and partly out the direct DMA window, on systems with > 2GB physical memory.
On Octane, force a nonzero _dma_mask value so that we do not risk trying to
handle a mapping partly in, and partly out the direct DMA window, on
systems with > 2GB physical memory.

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