dt-bindings: qcom: Document bindings for new MSM8916 devices

Document the new samsung,a3u/a5u-eur and longcheer,l8150
device tree bindings used in their device trees.

Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>