dt-bindings: soc: tegra-pmc: Add ID for Tegra PMC 32 kHz blink clock

Tegra PMC has blink functionality that allows 32 kHz clock out to
blink pin of the Tegra.

This patch adds id for this blink clock to use for enabling or
disabling blink output through device tree.

Tested-by: Dmitry Osipenko <digetx@gmail.com>
Reviewed-by: Dmitry Osipenko <digetx@gmail.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sowjanya Komatineni <skomatineni@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>