i40e: use newer generic PM support instead of legacy PM callbacks

Stop using the old legacy PM support, since we now have stable support
for the newer generic PM callbacks.

This has several advantages. First, we no longer have to manage our
own pci_save_state() and power changes, as it's preferred to have the
PCI stack do this. Second, these routines get called for both hibernate
and suspend to ram, so we can have the driver properly handle all the
suspend/resume flows that it needs to.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>