doc: announce PCI resources map API removal

doc: announce PCI resources map API removal

The PCI resources map API (pci_map_resource/pci_unmap_resource) was
imposing use of Unix mmap flags while it does not make sense on Windows.
This API was only used to internally setup PCI devices in the PCI bus
driver and has no known external users.

Announce its removal in 20.11 with its associated structures.

The workaround implemented in the commit 9d2b24593724 ("pci: keep API
compatibility with mmap values") will be removed at the same time.

Signed-off-by: David Marchand <david.marchand@redhat.com>
Acked-by: Jerin Jacob <jerinj@marvell.com>
Acked-by: Gaetan Rivet <grive@u256.net>
Acked-by: Thomas Monjalon <thomas@monjalon.net>