PCI/P2PDMA: Remove reference to pci_p2pdma_map_sg()

Update Documentation/driver-api/pci/p2pdma.rst doc and remove references to
obsolete p2pdma mapping functions.

Fixes: 0d06132 ("PCI/P2PDMA: Remove pci_p2pdma_[un]map_sg()")
Link: https://lore.kernel.org/r/20231113180325.444692-1-tstruk@gmail.com
Signed-off-by: Tadeusz Struk <tstruk@gigaio.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
Cc: stable@kernel.org

Author: tstruk

Documentation/driver-api/pci/p2pdma.rst

@@ -83,19 +83,9 @@ this to include other types of resources like doorbells.
 Client Drivers
 --------------
 
-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