virtio-serial: Clean up virtser_bus_dev_print() output

virtio-serial: Clean up virtser_bus_dev_print() output

Old version looks like this in info qtree (last four lines):

          dev: virtconsole, id ""
            dev-prop: is_console = 1
            dev-prop: nr = 0
            dev-prop: chardev = <null>
            dev-prop: name = <null>
             dev-prop-int: id: 0
             dev-prop-int: guest_connected: 1
             dev-prop-int: host_connected: 0
             dev-prop-int: throttled: 0

Indentation is off, and "dev-prop-int" suggests these are properties
you can configure with -device, which isn't the case.  The other
buses' print_dev() callbacks don't do that.  For instance, PCI's
output looks like this:

        class Ethernet controller, addr 00:03.0, pci id 1af4:1000 (sub 1af4:0001)
        bar 0: i/o at 0xffffffffffffffff [0x1e]
        bar 1: mem at 0xffffffffffffffff [0xffe]
        bar 6: mem at 0xffffffffffffffff [0xfffe]

Change virtser_bus_dev_print() to that style.  Result:

          dev: virtconsole, id ""
            dev-prop: is_console = 1
            dev-prop: nr = 0
            dev-prop: chardev = <null>
            dev-prop: name = <null>
            port 0, guest on, host off, throttle off

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>