ARM: dts: Add MDM9615 dtsi

In order to support the Qualcomm MDM9615 SoC, add the SoC dtsi.

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Reviewed-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>