arm64: dts: qcom: msm8996: Add support for the Xiaomi MSM8996 platform

There are 5 Xiaomi devices with the MSM8996 SoC:

 - Mi 5 (gemini): MSM8996 + PMI8994
 - Mi Note 2 (scorpio): MSM8996 Pro + PMI8996
 - Mi 5s (capricorn): MSM8996 Pro + PMI8996
 - Mi Mix (lithium): MSM8996 Pro + PMI8996
 - Mi 5s Plus (natrium): MSM8996 Pro + PMI8996

These devices share a common board design with only a few differences.
Add support for the common board, as well as support for the Mi Note 2.

Signed-off-by: Yassine Oudjana <y.oudjana@protonmail.com>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20210901193214.250375-4-y.oudjana@protonmail.com