PCI: Delete unnecessary NULL pointer checks

The functions pci_dev_put(), pci_pme_wakeup_bus(), and put_device() return
immediately if their argument is NULL.  Thus the test before the call is
not needed.

Remove these unnecessary tests.

This issue was detected by using the Coccinelle software.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>