ARM: msm: dts: Set mode as DEVICE only for SDM429

Set mode as DEVICE mode for SDM429 as usb host mode is not
required to support.

Change-Id: I78cefaa0f7ff5681c5eecf71b62adae1864bde0d
Signed-off-by: Vijayavardhan Vennapusa <vvreddy@codeaurora.org>