arm64: tegra: Enable DPAUX for Tegra210 Smaug

The Tegra210 Smaug uses I2C6 for interfacing to various audio chips.
I2C6 shares pads with the DPAUX interface and to allow I2C6 to request
the pads owned by DPAUX, the DPAUX device needs to be enabled. Enable
DPAUX for Tegra210 Smaug.

Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>