ARM: dts: qcom: msm8974-hammerhead: add device tree bindings for ALS / proximity

This patch adds device tree bindings for the tsl2772 ALS / proximity
sensor for the LG Nexus 5 (hammerhead) phone.

Signed-off-by: Brian Masney <masneyb@onstation.org>
Signed-off-by: Jonathan Marek <jonathan@marek.ca>
Acked-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Signed-off-by: Andy Gross <andy.gross@linaro.org>