dt-bindings: tegra: Update compatible strings for Tegra flowctrl

Update the compatible strings for Tegra Flow Control driver to match
the device-tree source files for Tegra.

Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>