IB/hfi1: Move saving PCI values to a separate function

During PCIe initialization some registers' values from
PCI config space are saved in order to restore them later
(i.e. after reset). Restoring those value is done by a
function called restore_pci_variables, while saving them
is put directly into function hfi1_pcie_ddinit.
Move saving values to a separate function in the image
of restoring functionality.

Reviewed-by: Jakub Byczkowski <jakub.byczkowski@intel.com>
Reviewed-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Bartlomiej Dudek <bartlomiej.dudek@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>