pci: keep API compatibility with mmap values

pci: keep API compatibility with mmap values

The function pci_map_resource() returns MAP_FAILED in case of error.
When replacing the call to mmap() by rte_mem_map(),
the error code became NULL, breaking the API.
This function is probably not used outside of DPDK,
but it is still a problem for two reasons:
	- the deprecation process was not followed
	- the Linux function pci_vfio_mmap_bar() is broken for i40e

The error code is reverted to the Unix value MAP_FAILED.
Windows needs to define this special value (-1 as in Unix).
After proper deprecation process, the API could be changed again
if really needed.

Because of the switch from mmap() to rte_mem_map(),
another part of the API was changed: "int additional_flags"
are defined as "additional flags for the mapping range"
without mentioning it was directly used in mmap().
Currently it is directly used in rte_mem_map(),
that's why the values rte_map_flags must be mapped (sic) on the mmap ones
in case of Unix OS.

These are side effects of a badly defined API using Unix values.

Bugzilla ID: 503
Fixes: 2fd3567e5425 ("pci: use OS generic memory mapping functions")

Reported-by: David Marchand <david.marchand@redhat.com>
Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
Acked-by: Dmitry Kozlyuk <dmitry.kozliuk@gmail.com>
Tested-by: Lihong Ma <lihongx.ma@intel.com>