Update qcom,a53pll bindings for MSM8939 support:

 - Add optional operating-points-v2 property
 - Add MSM8939 specific compatible
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Link: https://lore.kernel.org/r/20210704024032.11559-4-shawn.guo@linaro.orgAcked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>