ide: delkin_cb: use generic power management

ide: delkin_cb: use generic power management

With the support of generic PM callbacks, drivers no longer need to use
legacy .suspend() and .resume() in which they had to maintain PCI states
changes and device's power state themselves. All required operations are
done by PCI core.

After converting it into generic model, suspend() became an empty function.
Hence, it is defined as NULL.

Compile-tested only.

Signed-off-by: Vaibhav Gupta <vaibhavgupta40@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>