PCI/pwrctrl: Create pwrctrl devices only when CONFIG_PCI_PWRCTRL is enabled

If devicetree describes power supplies related to a PCI device, we
unnecessarily created a pwrctrl device even if CONFIG_PCI_PWRCTL was not
enabled.

We only need pci_pwrctrl_create_device() when CONFIG_PCI_PWRCTRL is
enabled.  Compile it out when CONFIG_PCI_PWRCTRL is not enabled.

When pci_pwrctrl_create_device() creates and returns a pwrctrl device,
pci_scan_device() doesn't enumerate the PCI device. It assumes the pwrctrl
core will rescan the bus after turning on the power. However, if
CONFIG_PCI_PWRCTRL is not enabled, the rescan never happens, which breaks
PCI enumeration on any system that describes power supplies in devicetree
but does not use pwrctrl.

Jim reported that some brcmstb platforms break this way.  The brcmstb
driver is still broken if CONFIG_PCI_PWRCTRL is enabled, but this commit at
least allows brcmstb to work when it's NOT enabled.

Fixes: 957f40d ("PCI/pwrctrl: Move creation of pwrctrl devices to pci_scan_device()")
Reported-by: Jim Quinlan <[email protected]>
Link: https://lore.kernel.org/r/CA+-6iNwgaByXEYD3j=-+H_PKAxXRU78svPMRHDKKci8AGXAUPg@mail.gmail.com
Signed-off-by: Manivannan Sadhasivam <[email protected]>
[bhelgaas: commit log]
Signed-off-by: Bjorn Helgaas <[email protected]>
Reviewed-by: Lukas Wunner <[email protected]>
Cc: [email protected]	# v6.15
Link: https://patch.msgid.link/[email protected]

Author: Mani-Sadhasivam

drivers/pci/probe.c

@@ -2508,6 +2508,7 @@ bool pci_bus_read_dev_vendor_id(struct pci_bus *bus, int devfn, u32 *l,
 }
 EXPORT_SYMBOL(pci_bus_read_dev_vendor_id);
 
+#if IS_ENABLED(CONFIG_PCI_PWRCTRL)
 static struct platform_device *pci_pwrctrl_create_device(struct pci_bus *bus, int devfn)
 {
 	struct pci_host_bridge *host = pci_find_host_bridge(bus);
@@ -2537,6 +2538,12 @@ static struct platform_device *pci_pwrctrl_create_device(struct pci_bus *bus, in
 
 	return pdev;
 }
+#else
+static struct platform_device *pci_pwrctrl_create_device(struct pci_bus *bus, int devfn)
+{
+	return NULL;
+}
+#endif
 
 /*
  * Read the config data for a PCI device, sanity-check it,