ARM: dts: qcom: msm8974: Add USB gadget nodes

Add the necessary nodes for USB gadget on MSM8974 and enable these for
Honami.

Signed-off-by: Bjorn Andersson <bjorn.andersson@sonymobile.com>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>