PCI: brcmstb: Fix potential premature regulator disabling

Our system for enabling and disabling regulators is designed to work only
on the port driver below the root complex.  The conditions to discriminate
for this case should be the same when we are adding or removing the bus.
Without this change the regulators may be disabled prematurely when a bus
further down the tree is removed.

Fixes: 9e6be01 ("PCI: brcmstb: Enable child bus device regulators from DT")
Signed-off-by: Jim Quinlan <james.quinlan@broadcom.com>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>

Author: jamesequinlan

drivers/pci/controller/pcie-brcmstb.c

@@ -1440,7 +1440,7 @@ static void brcm_pcie_remove_bus(struct pci_bus *bus)
 	struct subdev_regulators *sr = pcie->sr;
 	struct device *dev = &bus->dev;
 
-	if (!sr)
+	if (!sr || !bus->parent || !pci_is_root_bus(bus->parent))
 		return;
 
 	if (regulator_bulk_disable(sr->num_supplies, sr->supplies))