dt-bindings: qcom: clocks: Add SDXPRAIRIE V2 clock bindings

Add the compatible string for the SDXPRAIRIE V2 global clock
controller to the clock binding documentation.

Change-Id: I137793f7b71680f682e2e740dfccf68c0df5623c
Signed-off-by: Naveen Yadav <naveenky@codeaurora.org>