ARM: dts: qcom: msm8974: Add Sony Xperia Z2 Tablet

This adds a basic DTS file for the Sony Xperia Z2 Tablet, containing
definitions for regulators, eMMC/SD-card, USB, WiFi, Touchscreen,
charger, backlight, coincell and buttons.

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>