tty: pdc_cons, free tty_driver upon failure

pdc_console_tty_driver_init() does not free the allocated tty driver in
case tty_register_driver() fails. Add one tty_driver_kref_put() to the
error path.

Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
Cc: Helge Deller <deller@gmx.de>
Cc: linux-parisc@vger.kernel.org
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210723074317.32690-9-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>