PCI: pciehp: Make various functions void since they can't fail

These functions:

  pcie_enable_notification()
  pciehp_power_off_slot()
  pciehp_get_power_status()
  pciehp_get_attention_status()
  pciehp_set_attention_status()
  pciehp_get_latch_status()
  pciehp_get_adapter_status()
  pcie_write_cmd()

now always return success, so this patch makes them void and drops the
error-checking code in their callers.

No functional change.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
diff --git a/drivers/pci/hotplug/pciehp_pci.c b/drivers/pci/hotplug/pciehp_pci.c
index 0e0d0f7..1983551 100644
--- a/drivers/pci/hotplug/pciehp_pci.c
+++ b/drivers/pci/hotplug/pciehp_pci.c
@@ -78,7 +78,7 @@
 
 int pciehp_unconfigure_device(struct slot *p_slot)
 {
-	int ret, rc = 0;
+	int rc = 0;
 	u8 bctl = 0;
 	u8 presence = 0;
 	struct pci_dev *dev, *temp;
@@ -88,9 +88,7 @@
 
 	ctrl_dbg(ctrl, "%s: domain:bus:dev = %04x:%02x:00\n",
 		 __func__, pci_domain_nr(parent), parent->number);
-	ret = pciehp_get_adapter_status(p_slot, &presence);
-	if (ret)
-		presence = 0;
+	pciehp_get_adapter_status(p_slot, &presence);
 
 	/*
 	 * Stopping an SR-IOV PF device removes all the associated VFs,