tty_audit: make icanon a bool

Use bool for tty_audit_buf::icanon in favor of ugly bitfields. And get
rid of "!!" as that is completely unnecessary.

Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20230621101611.10580-5-jirislaby@kernel.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>