ALSA: docs: Remove snd_dma_pci_data() usage in documentation

              /* pre-allocation of buffers */

              /* NOTE: this may fail */

              snd_pcm_lib_preallocate_pages_for_all(pcm, SNDRV_DMA_TYPE_DEV,

                                                    snd_dma_pci_data(chip->pci),

                                                    &chip->pci->dev,

                                                    64*1024, 64*1024);

              return 0;

      }

::

  snd_pcm_lib_preallocate_pages_for_all(pcm, SNDRV_DMA_TYPE_DEV,

                                        snd_dma_pci_data(chip->pci),

                                        &chip->pci->dev,

                                        64*1024, 64*1024);

It will allocate a buffer up to 64kB as default. Buffer management

::

  snd_pcm_lib_preallocate_pages_for_all(pcm, SNDRV_DMA_TYPE_DEV,

                                        snd_dma_pci_data(pci), size, max);

                                        &pci->dev, size, max);

where ``size`` is the byte size to be pre-allocated and the ``max`` is

the maximum size to be changed via the ``prealloc`` proc file. The

:c:func:`snd_pcm_lib_preallocate_pages()` or

:c:func:`snd_pcm_lib_preallocate_pages_for_all()` with

``SNDRV_DMA_TYPE_DEV_SG`` in the PCM constructor like other PCI

pre-allocator. You need to pass ``snd_dma_pci_data(pci)``, where pci is

pre-allocator. You need to pass ``&pci->dev``, where pci is

the :c:type:`struct pci_dev <pci_dev>` pointer of the chip as

well.

::

  snd_pcm_lib_preallocate_pages_for_all(pcm, SNDRV_DMA_TYPE_DEV_SG,

                                        snd_dma_pci_data(pci), size, max);

                                        &pci->dev, size, max);

The ``struct snd_sg_buf`` instance is created as

``substream->dma_private`` in turn. You can cast the pointer like: