ARM: dts: qcom-msm8960-cdp: Add RNG device tree node

Add the necessary DT node to probe the rng driver on
msm8960-cdp platform.

Signed-off-by: Stanimir Varbanov <svarbanov@mm-sol.com>
Tested-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Kumar Gala <galak@codeaurora.org>