Honor maxsegsz of less than a page size in a DMA tag. Previously it

used to return PAGE_SIZE without respect to restrictions of a DMA tag.
This affected all of the busdma load functions that use
_bus_dmamap_loader_buffer() as their back-end.

Reviewed by:	scottl (long a ago)
Approved by:	re (hrs)

sys/powerpc/powerpc/busdma_machdep.c

@@ -418,6 +418,8 @@ bus_dmamap_load_buffer(bus_dma_tag_t dmat, bus_dma_segment_t segs[],
 		 * Compute the segment size, and adjust counts.
 		 */
 		sgsize = PAGE_SIZE - ((u_long)curaddr & PAGE_MASK);
+		if (sgsize > dmat->maxsegsz)
+			sgsize = dmat->maxsegsz;
 		if (buflen < sgsize)
 			sgsize = buflen;