Theory has it that with the LinuxKPI alloc code now providing
physically contiguous memory we should be fine so we can remove
the entire compat code.
For this to happen busdma bounce needs to be able to bounce multiple
contiguous pages with nseg=1. Removing this code the LinuxKPI debug
counter about failed mappings raises quickly. See the discussion in
D45813 for some more info.
Older Intel cards do have a 36bit DMA limit, rtw88 seems to still have
a 32bit limit despite PCIe.
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