arm64: dts: qcom: msm8998: Introduce support for Sony Yoshino platform

This commit introduces support for the Sony Yoshino platform, using
the MSM8998 SoC, including:
- Sony Xperia XZ1 (codename Poplar),
- Sony Xperia XZ1 Compact (codename Lilac),
- Sony Xperia XZ Premium (codename Maple).

All of the three aforementioned smartphones are sharing a 99%
equal board configuration, with very small differences between
each other, which is the reason for the introduction of a common
msm8998-sony-xperia-yoshino DT.

This base configuration includes regulators and project-wide pin
configurations and it's made to boot to a serial console.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@somainline.org>
Reviewed-by: Marijn Suijten <marijn.suijten@somainline.org>
Reviewed-by: Konrad Dybcio <konrad.dybcio@somainline.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20210909123733.367248-1-angelogioacchino.delregno@somainline.org