Nvidia's Tegra20 have the SPI (SFLASH) controller to
interface with spi flash device which is used for system
boot. Add DT entry for this controller.
Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
[swarren: move sflash node to keep file sorted]
Signed-off-by: Stephen Warren <swarren@nvidia.com>