PCI: layerscape: Call dw_pcie_setup_rc() from ls_pcie_host_init()

We called dw_pcie_setup_rc() from the ls1021a host init function, but not
from the common ls_pcie_host_init() function, so platforms other than
ls1021a still depended on initialization by the bootloader.

Call dw_pcie_setup_rc() from ls_pcie_host_init() to reduce dependencies on
the bootloader.

Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Roy Zang <tie-fei.zang@freescale.com>