video: fbdev: skeletonfb: Convert to generic power management

PCI-specific power management (pci_driver.suspend and pci_driver.resume) is
deprecated.  If drivers implement power management, they should use the
generic power management framework, not the PCI-specific hooks.

Convert the sample code to use the generic power management framework.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Helge Deller <deller@gmx.de>