console: Fix isatty on a fd that refers to /dev/console

The problem was the flag D_TTY, meaning that device is TTY, not
being passed to device_create.

Signed-off-by: Raphael S. Carvalho <raphaelsc@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>