MFi386: r274398

  Move NFS and TFTP filesystems before the synthetic filesystems (bzip,
  gzip, and split).
When doing busdma sync ops for BUSDMA_COHERENT memory, there is no need
for cache maintenance operations, but ensure that all prior writes have
reached memory when doing a PREWRITE sync.

Submitted by:	Michal Meloun <meloun@miracle.cz>