ARM: dts: msm: Fix the source of UFS device reference clock for MSM8996

As UFS device reference clock is sourced from LNBBCLK (not from BBCLK1) via
CXO2, this change makes the correction.

Change-Id: I92e10055fae20156f968e03447c2f131c10b0e3c
Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>