devlink: Add devlink health show command

devlink: Add devlink health show command

Add devlink health show command which displays status and configuration
info on a specific reporter on a device or dump the info on all
reporters on all devices. Add helper functions to display status and
dump's time stamp.
Example:
$ devlink health show pci/0000:00:09.0 reporter tx
pci/0000:00:09.0:
 name tx
  state healthy error 0 recover 1 last_dump_date 2019-02-14 last_dump_time 10:10:10 grace_period 600 auto_recover true
$ devlink health show pci/0000:00:09.0 reporter tx -jp
{
 "health":{
  "pci/0000:00:0a.0":[
     {
     "name":"tx",
     "state":"healthy",
     "error":0,
     "recover":1,
     "last_dump_date":"2019-Feb-14",
     "last_dump_time":"10:10:10",
     "grace_period":600,
     "auto_recover":true
    }
  ]
}

Signed-off-by: Aya Levin <ayal@mellanox.com>
Reviewed-by: Moshe Shemesh <moshe@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David Ahern <dsahern@gmail.com>