bus: add device arguments name parsing

bus: add device arguments name parsing

For device probe and iterator, devargs name was key information,
parsed by rte_devargs_parse. In legacy parser, devargs name was
extracted after bus name:
  bus:name,kv_arguments,,,
Example:
  pci:83:00.0,arguments,...
  vdev:pcap0,...

To be compatible with legacy parser, this patch introduces new
bus driver API devargs_parse to parse devargs and update devargs name.
If devargs_parse not implemented by bus driver, the new syntax parser
rte_devargs_layers_parse default will resolve devargs name from bus's
"name" argument.

Different bus driver might choose different keys from arguments with
unified format. The PCI bus implementation fills the devargs name with
the "addr" argument, example:
 -a bus=pci,addr=83:00.0/class=eth/driver=mlx5,...
    name: 0000:03:00.0
 -a bus=vdev,name=pcap0/class=eth/driver=pcap,...
    name:pcap0

Signed-off-by: Xueming Li <xuemingl@nvidia.com>
Reviewed-by: Gaetan Rivet <grive@u256.net>