PCI: histb: Drop unnecessary root_bus_nr setting

Function dw_pcie_host_init() already initializes the root_bus_nr field
of 'struct pcie_port', so the -1 assignment prior to calling
dw_pcie_host_init() in platform specific driver is not really needed.
Drop it.
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Jianguo Sun <sunjianguo1@huawei.com>

drivers/pci/controller/dwc/pcie-histb.c

@@ -420,7 +420,6 @@ static int histb_pcie_probe(struct platform_device *pdev)
 		phy_init(hipcie->phy);
 	}
 
-	pp->root_bus_nr = -1;
 	pp->ops = &histb_pcie_host_ops;
 
 	platform_set_drvdata(pdev, hipcie);