z85230: spinlock logic

At some point someone added a spin_lock(&dev->lock) to the IRQ handler for
the Z85230 driver.  This actually correctly fixes a bug but the necessary
changes to remove the chan->lock calls in the event handlers were not made
(c->lock is the same lock).

Simona Dascenzo reported the problem with the driver and this patch should
fix the problem he found.

Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jeff Garzik <jeff@garzik.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>