ARM: tegra: add Tegra Note 7 device tree

Tegra Note 7 is a consumer tablet embedding a Tegra 4 SoC with 1GB RAM
and a 720p panel.

The following hardware is enabled by this device tree: UART, eMMC, USB
(needs external power), PMIC, backlight, DSI panel, keys.

SD card, HDMI, charger, self-powered USB, audio, wifi, bluetooth are not
yet supported but might be by future patches (likely in that order).

Touch panel, sensors & cameras will probably never be supported.

Pinctrl is not set yet, as the bootloader-provided values allow us to
use the currently supported hardware.

Initrd addresses are hardcoded to match the static values used by the
bootloader, since it won't add them for us. All the same, a kernel
command-line is provided to replace the one passed by the bootloader
which is filled with garbage.

Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
[treding@nvidia.com: DT fixes, DSI panel support]
Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Stephen Warren <swarren@nvidia.com>