- Move busdma_lock_mutex to subr_bus_dma.c.
- Move _busdma_lock_dflt to subr_bus_dma.c. This function was named a
couple of different things previously. It is not a public API but
an internal helper used in place of a NULL pointer. The prototype
is in <sys/bus_dma.h> as not all backends include
<sys/bus_dma_internal.h>.
Reviewed by: kib
Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D33694
7def1e10b3