PCI/P2PDMA: Remove reference to pci_p2pdma_map_sg()

Client Drivers

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A client driver typically only has to conditionally change its DMA map

routine to use the mapping function :c:func:`pci_p2pdma_map_sg()` instead

of the usual :c:func:`dma_map_sg()` function. Memory mapped in this

way does not need to be unmapped.

The client may also, optionally, make use of

:c:func:`is_pci_p2pdma_page()` to determine when to use the P2P mapping

functions and when to use the regular mapping functions. In some

situations, it may be more appropriate to use a flag to indicate a

given request is P2P memory and map appropriately. It is important to

ensure that struct pages that back P2P memory stay out of code that

does not have support for them as other code may treat the pages as

regular memory which may not be appropriate.

A client driver only has to use the mapping API :c:func:`dma_map_sg()`

and :c:func:`dma_unmap_sg()` functions as usual, and the implementation

will do the right thing for the P2P capable memory.

Orchestrator Drivers