PCI: dwc: designware: Fix style errors in pcie-designware.c

No functional change. Fix all checkpatch warnings and check errors in
pcie-designware.c

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-By: Joao Pinto <jpinto@synopsys.com>