dt-bindings: clock: tegra: Add sor1_out clock

The sor1_src clock implemented on Tegra210 is modelled the wrong way
around, which causes some issues with HDMI and DP support. This clock
implementation is provided by BPMP on Tegra186, which models this in
a more correct way. Since this introduces incompatibilities between
the two SoC generations which we want to avoid, the Tegra210 will be
fixed in subsequent patches.

This change adds sor1_out as an alias for sor1_src.

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