- Don't try to allocate mappings of less than a PAGE_SIZE in MGA DMA code.

- Comment out the "is this mapping/bufs in allocated AGP" bits in BSD
    because they break mga (which uses AGP allocation that doesn't track
    entries). It's not a security issue when we still have the related
    ioctls marked root-only.
- Apply some power-of-two alignment restrictions to hopefully avoid some
    panicing in bad cases of drm_pci_alloc() on FreeBSD.
- Add verbosity to some error handling that I found useful while debugging.