ARM: tegra: add Venice2 (Tegra124) board

These are the board files for Venice2 (Tegra124), plus the AS3722 PMIC
files. PMIC init will be moved to pmic_common_init later.

This builds/boots on Venice2, SPI/MMC/USB/I2C all work. Audio, display
and WB/LP0 are not supported yet.

Signed-off-by: Tom Warren <twarren@nvidia.com>
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Tested-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Tom Warren <twarren@nvidia.com>