ARM: dts: qcom: msm8974-hammerhead: add USB OTG support

Add the device tree bindings for USB OTG support. Driver was tested
using on a LG Nexus 5 (hammerhead) phone. This patch is based on work
from Jonathan Marek and from the other msm8974 devices.

Signed-off-by: Brian Masney <masneyb@onstation.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>