dm: pci: return the real controller in pci_bus_to_hose()

for the legacy PCI driver, the function pci_bus_to_hose() returns
the real PCIe controller. To keep consistency, this function is
changed to return the PCIe controller pointer of the root bus
instead of the current PCIe bus.

Signed-off-by: Minghuan Lian <Minghuan.Lian@nxp.com>
Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: York Sun <york.sun@nxp.com>