ARM: dts: msm: Add child node entry for CPE NTN3 i2c client on sdxlemur

In order to access NTN3 switch registers add i2c client properties.
By accessing these registers, root complex driver can toggle NTN3
GPIOs tied to downstream endpoint reset. i2c interface is also used
to dump NTN3 registers for debugging PCIe link related issues.

Change-Id: Ib7e85c463a0072dd2919559ab4d701d5eb42f400