pause: add --json support

No change in normal text output:

 # ./ethtool  -a eth0
Pause parameters for eth0:
Autonegotiate:	on
RX:		on
TX:		on
RX negotiated: on
TX negotiated: on

JSON:

 # ./ethtool --json -a eth0
[ {
        "ifname": "eth0",
        "autonegotiate": true,
        "rx": true,
        "tx": true,
        "negotiated": {
            "rx": true,
            "tx": true
        }
    } ]

v2:
 - restructure show_bool() so we can use its logic for show_bool_val()

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Michal Kubecek <mkubecek@suse.cz>
3 files changed