arm64: dts: exynos: Add extcon property for TM2 and TM2E

Since commit 9840354f ("usb: dwc3: Add dual-role support") dwc3
node requires extcon property to be initialized as OTG mode and it
supports dual-role mode operation.

Signed-off-by: Dongwoo Lee <dwoo08.lee@samsung.com>
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>