Do not leave dirty cache lines behind if bus_dmamap_sync was called to invalidate memory chunk that starts or ends in the middle of cache line.
Do not leave dirty cache lines behind if bus_dmamap_sync was called
to invalidate memory chunk that starts or ends in the middle of
cache line.

This was responsible for one half of the problem preventing umass
to work reliably on some MIPS32 platforms. USBng needs to stop
sharing cache lines between DMA-able memory and other structures
to cure the other half.

Discussed with: imp, gonzo

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase