Now that uvm_pglistalloc() does not lose on large memory gaps, do not restrict the memory allocation range in _dmamem_alloc().
Now that uvm_pglistalloc() does not lose on large memory gaps, do not
restrict the memory allocation range in _dmamem_alloc().

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