pci: move resource mapping to the PCI bus

pci: move resource mapping to the PCI bus

As reported during 20.08 work for Windows, the pci_map_resource API was
built with the assumption that its flags would be passed to mmap().

This introduced a regression when adding the rte_mem_map API as reported
in the workaround commit 9d2b24593724 ("pci: keep API compatibility with
mmap values").

This API was only used in the PCI bus code, so move it there.

There is no code change happening during the move.
The only change is in the pci_map_resource description where the
additional flags are now documented as rte_mem_map API flags:
- *      The additional flags for the mapping range.
+ *      The additional rte_mem_map() flags for the mapping range.

Signed-off-by: David Marchand <david.marchand@redhat.com>
Acked-by: Andrew Rybchenko <arybchenko@solarflare.com>
Acked-by: Ray Kinsella <mdr@ashroe.eu>