LinuxKPI: implement dma_sync_single_for_*, apply to (un)map single/sg

Implement dma_sync_single_for_{cpu,device} translating the Linux
DMA_ flags to BUS_DMASYNC_ combinations. Make map_single/unmap_single*
functions call the respective sync function. Apply the same logic to
the scatter-gather list map/unmap functions.

Sponsored by: The FreeBSD Foundation
MFC after: 3 days
Reviewed by: hselasky
Differential Revision: https://reviews.freebsd.org/D32255