Do not duplicate common tty_port_hangup code. Use it instead.

Also do not unset ASYNC_NORMAL_ACTIVE and wake up from the
tty_hangup() caller. It makes no sense since we don't check that
flag in sleepers. tty_port_hangup() performed later will do the
right job.
Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>