vdpa: Allow for printing negotiated features of a device

vdpa: Allow for printing negotiated features of a device

When reading the configuration of a vdpa device, check if the
VDPA_ATTR_DEV_NEGOTIATED_FEATURES is available. If it is, parse the
feature bits and print a string representation of each of the feature
bits.

We keep the strings in two different arrays. One for net device related
devices and one for generic feature bits.

In this patch we parse only net device specific features. Support for
other devices can be added later. If the device queried is not a net
device, we print its bit number only.

Examples:
1. Standard presentation
$ vdpa dev config show vdpa-a
vdpa-a: mac 00:00:00:00:88:88 link up link_announce false max_vq_pairs 2 mtu 9000
  negotiated_features CSUM GUEST_CSUM MTU MAC HOST_TSO4 HOST_TSO6 STATUS \
CTRL_VQ MQ CTRL_MAC_ADDR VERSION_1 ACCESS_PLATFORM

2. json output
$ vdpa -j dev config show vdpa-a
{"config":{"vdpa-a":{"mac":"00:00:00:00:88:88","link":"up","link_announce":false,\
"max_vq_pairs":2,"mtu":9000,"negotiated_features":["CSUM","GUEST_CSUM",\
"MTU","MAC","HOST_TSO4","HOST_TSO6","STATUS","CTRL_VQ","MQ","CTRL_MAC_ADDR",\
"VERSION_1","ACCESS_PLATFORM"]}}}

3. Pretty json
$ vdpa -jp dev config show vdpa-a
{
    "config": {
        "vdpa-a": {
            "mac": "00:00:00:00:88:88",
            "link ": "up",
            "link_announce ": false,
            "max_vq_pairs": 2,
            "mtu": 9000,
            "negotiated_features": [
"CSUM","GUEST_CSUM","MTU","MAC","HOST_TSO4","HOST_TSO6","STATUS","CTRL_VQ",\
"MQ","CTRL_MAC_ADDR","VERSION_1","ACCESS_PLATFORM" ]
        }
    }
}

Reviewed-by: Si-Wei Liu<si-wei.liu@oracle.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Eli Cohen <elic@nvidia.com>
Signed-off-by: David Ahern <dsahern@kernel.org>