Add in missing qcom,dsi-phy-regulator-ldo-mode to the 28nm DSI PHY.
When converting from .txt to .yaml we missed this one.

Fixes: 4dbe55c9 ("dt-bindings: msm: dsi: add yaml schemas for DSI bindings")
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/516205/
Link: https://lore.kernel.org/r/20221229124438.504770-2-bryan.odonoghue@linaro.orgSigned-off-by: Abhinav Kumar <quic_abhinavk@quicinc.com>