tty: Fix spinlock flavor in non-atomic __tty_hangup()

__tty_hangup() and tty_vhangup() cannot be called from atomic context,
so locks do not need to preserve the interrupt state (although,
still disable interrupts).

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Acked-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>