PCI: Remove unnecessary returns

Remove unnecessary "return" statements at the end of void functions.  No
functional change intended.

Link: https://lore.kernel.org/r/20190825221039.6977-1-kw@linux.com
Link: https://lore.kernel.org/r/20190826095143.21353-1-kw@linux.com


Signed-off-by: Krzysztof Wilczynski <kw@linux.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>