arm64: dts: qcom: msm8916: add xo clocks to rpmcc and a53pll

Both a53pll and rpmcc make use of xo as a clock parent. Add it to the
respective device nodes.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Stephan Gerhold <stephan@gerhold.net>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20220620010519.1533364-1-dmitry.baryshkov@linaro.org