arm64: tegra: Add supply for temperature sensor on P2888

The VCC supply property is not populated for the temperature sensor on
the P2888 board and so the following warning is observed on boot ...

 lm90 0-004c: 0-004c supply vcc not found, using dummy regulator

On the P2888 board, the VCC supply for the temperature sensor is
connected to the 'vdd_1v8ls' rail. Add the 'vcc-supply' property for
the temperature sensor to prevent this warning message from occurring.

Fixes: 8b457812 ('arm64: tegra: Add temperature sensor on P2888')
Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>