ARM: dts: msm: add pci DT nodes for PCIe switch for sdxlemur CPE

If there is a switch connected to PCIe root complex, the
devicetree hierarchy needs to correctly reflect the physical
connection. Add pci DT nodes for each switch device such as
switch upstream and downstream ports for sdxlemur CPE.

Change-Id: I04ddd33adc67f0ec689d014cd00ed5fa26d02a89