arm64: dts: qcom: sagit: add initial device tree for sagit

New device support - Xiaomi Mi6 phone

What works:
- storage
- usb
- power regulators

Signed-off-by: Dzmitry Sankouski <dsankouski@gmail.com>
Reviewed-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Reviewed-by: Konrad Dybcio <konra.dybcio@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20221112203300.536010-3-dsankouski@gmail.com