nvme-print: nvme list -o json fix

nvme-print: nvme list -o json fix

Bellow error log will be triggered on non pcie transport, so only print the
ProductName for pcie transport, also add print "\n" and json_free_object fix

Failed to open /sys/class/nvme/nvme1/device/subsystem_vendor with errno No such file or directory
Failed to open /sys/class/nvme/nvme1/device/subsystem_device with errno No such file or directory
Failed to open /sys/class/nvme/nvme1/device/vendor with errno No such file or directory
Failed to open /sys/class/nvme/nvme1/device/device with errno No such file or directory
Failed to open /sys/class/nvme/nvme1/device/class with errno No such file or directory
{
  "Devices" : [
    {
      "NameSpace" : 1,
      "DevicePath" : "/dev/nvme1n1",
      "Firmware" : "4.18.0-1",
      "Index" : 1,
      "ModelNumber" : "Linux",
      "ProductName" : "NULL",
      "SerialNumber" : "eb4695bf0da275a3",
      "UsedBytes" : 268435456000,
      "MaximumLBA" : 524288000,
      "PhysicalSize" : 268435456000,
      "SectorSize" : 512
    }
  ]
}

Reported-by: Justin Tee  <justin.tee@broadcom.com>
Signed-off-by: Yi Zhang <yi.zhang@redhat.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>