dt-bindings: arm: qcom: document sc7280 and villager board

This adds a LTE skus for Chromebook Villager to the yaml.

Signed-off-by: Jimmy Chen <jinghung.chen3@hotmail.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/SG2PR03MB5006CE1EB9BFD95511133CA6CC949@SG2PR03MB5006.apcprd03.prod.outlook.com