arm64: dts: sdm850: Add OPP tables for 2.84 and 2.96GHz

Running cpufreq-hw driver on Lenovo Yoga C630 laptop, the following
warning messages will be seen.

[    3.415340] cpu cpu4: Voltage update failed freq=2841600
[    3.418755] cpu cpu4: failed to update OPP for freq=2841600
[    3.422949] cpu cpu4: Voltage update failed freq=2956800
[    3.427086] cpu cpu4: failed to update OPP for freq=2956800

This is because the cpufreq-hw lookup table of SDM850 provides these two
set-points, but they are missing from OPP table in DT.  Let's create
sdm850.dtsi to add the OPP for them, so that the warning will be gone.

Signed-off-by: Steev Klimaszewski <steev@kali.org>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Link: https://lore.kernel.org/r/20210112090640.20062-1-shawn.guo@linaro.org
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>