The fallback S/G buffer allocation for x86 used the addresses deduced
from the page allocations blindly.  It broke the allocations on IOMMU
and made us to work around with a hackish DMA ops check.

For cleaning up those messes, this patch switches to the proper DMA
mapping API usages with the standard sg-table instead.

By introducing the sg-table, the address table isn't needed, but for
keeping the original allocation sizes for freeing, replace it with the
array keeping the number of pages.

The get_addr callback is changed to use the existing one for
non-contiguous buffers.  (Also it's the reason sg_table is put at the
beginning of struct snd_dma_sg_fallback.)

And finally, the hackish workaround that checks the DMA ops is
dropped now.

Link: https://patch.msgid.link/20240912155227.4078-3-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>