ARM: dt: Add SD controller configuration to Tegra Cardhu

Cardhu uses Tegra's SD ports as follows:
SDMMC1: User SD slot, with GPIOs for power, CD, and WP.
SDMMC2: Not used
SDMMC3: WiFi (currently disabled pending future investigation)
SDMMC4: Internal eMMC

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Olof Johansson <olof@lixom.net>