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.