pci: layerscape: move kernel DT fixup to a separate file

To make the layerscape pcie driver clear, move the kernel DT fixup
code from pcie_layerscape.c to pcie_layerscape_fixup.c.

Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: York Sun <york.sun@nxp.com>
diff --git a/drivers/pci/Makefile b/drivers/pci/Makefile
index 86717a4..42174f9 100644
--- a/drivers/pci/Makefile
+++ b/drivers/pci/Makefile
@@ -32,4 +32,5 @@
 obj-$(CONFIG_WINBOND_83C553) += w83c553f.o
 obj-$(CONFIG_PCIE_DW_MVEBU) += pcie_dw_mvebu.o
 obj-$(CONFIG_PCIE_LAYERSCAPE) += pcie_layerscape.o
+obj-$(CONFIG_PCIE_LAYERSCAPE) += pcie_layerscape_fixup.o
 obj-$(CONFIG_PCI_XILINX) += pcie_xilinx.o