atm: horizon: Fix irq release error

atm_dev_register() can fail here and passed parameters to free irq
which is not initialised. Initialization of 'dev->irq' happened after
the 'goto out_free_irq'. So using 'irq' insted of 'dev->irq' in
free_irq().

Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>