- When bus_dmamem_alloc is used, the bus_dmamap_t is usually set to NULL, so we were never actually freeing any dma memory allocations done via iwm_dma_contig_alloc(). So we should check dma->vaddr instead of dma->map here.
- Also, the dmamap is actually supposed to be invalidated as part of bus_dmamem_free(), so bus_dmamap_destroy() is never needed here.
Obtained from: DragonFlyBSD ef2b29a7ba6ca8a9d2c82ab591c0622227ff84cb