igb: Fix WARN_ONCE on runtime suspend

The runtime_suspend device callbacks are not supposed to save
configuration state or change the power state. Commit fb29f76cc566
("igb: Fix an issue that PME is not enabled during runtime suspend")
changed the driver to not save configuration state during runtime
suspend, however the driver callback still put the device into a
low-power state. This causes a warning in the pci pm core and results in
pci_pm_runtime_suspend not calling pci_save_state or pci_finish_runtime_suspend.

Fix this by not changing the power state either, leaving that to pci pm
core, and make the same change for suspend callback as well.

Also move a couple of defines into the appropriate header file instead
of inline in the .c file.

Fixes: fb29f76cc566 ("igb: Fix an issue that PME is not enabled during runtime suspend")
Signed-off-by: Arvind Sankar <niveditas98@gmail.com>
Reviewed-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>