tty: core: Add driver name to invalid device registration message
Include the driver name in the tty_register_device_attr() error
message for invalid index.
Note that tty_err() cannot be used here because there is no tty;
use pr_err().
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>