cmd: improve coninfo output formatting

cmd: improve coninfo output formatting

Device name are typically longer than 8 characters. This leads to ragged
output.
Only the I and O bit of the device flags are of interest for the user.
Writing a hexadecimal number is just confusing.

Before the patch the output looked like this:

    => coninfo
    List of available devices:
    pl011@9000000 00000007 IO stdin stdout stderr
    serial   00000003 IO
    usbkbd   00000001 I.

With the patch the output looks like this:

    => coninfo
    List of available devices
    |-- pl011@9000000 (IO)
    |   |-- stdin
    |   |-- stdout
    |   |-- stderr
    |-- serial (IO)
    |-- usbkbd (I)

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Simon Glass <sjg@chromium.org>