PCI: shpchp: Make shpchp_unconfigure_device() void

PCI: shpchp: Make shpchp_unconfigure_device() void

shpchp_unconfigure_device() always returned 0, so there's no reason for a
return value.  In addition, remove_board() checked the return value for
possible error which is unnecessary.

Convert shpchp_unconfigure_device() to a void function and remove the
return value check.  This addresses the following Coccinelle warning:

  drivers/pci/hotplug/shpchp_pci.c:66:5-7: Unneeded variable: "rc".  Return "0" on line 86

Link: https://lore.kernel.org/r/20200521190457.1066600-1-kw@linux.com
Signed-off-by: Krzysztof Wilczynski <kw@linux.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>