LinuxKPI: dma-mapping.h unify "mask" and "dma_mask"

In some places we are using "mask" and others "dma_mask" for the
same thing. Harmonize the various places to "dma_mask" as used in
linux_pci.c. For the declaration remove the argument names to
avoid the entire problem.

This is in preparation for an upcoming change.
No functional changes intended.

Sponsored by: The FreeBSD Foundation
MFC after: 5 days