misc/phantom.c: use generic power management

misc/phantom.c: 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.

Driver needs to do only device-specific operations.

Compile-tested only.

Signed-off-by: Vaibhav Gupta <vaibhavgupta40@gmail.com>
Link: https://lore.kernel.org/r/20200629081531.214734-5-vaibhavgupta40@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>