ARM: dts: msm: Add qcom_gadget node for SA415

Add qcom_gadget node to enable usb composition at
boot time on SA415m. Allow changing the default pid
using "usb_pid" parameter from kernel command line.

Change-Id: I9a3963c68b0b09deec3457b54e59ca8eb03dfb3f
Signed-off-by: Aniket Randive <arandive@codeaurora.org>