NET: irda, remove unnecessary checks

Stanse found a potential null dereference in ircomm_tty_close
and ircomm_tty_hangup. There is a check for tty being NULL,
but it is dereferenced earlier. But it is bogus, the tty cannot
be NULL, so remove the !tty checks.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Samuel Ortiz <samuel@sortiz.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Alan Cox <alan@linux.intel.com>
Cc: Greg Kroah-Hartman <gregkh@suse.de>
Cc: netdev@vger.kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>