tegra: fdt: Add clock bindings for Tegra2 Seaboard

Add the definition of the oscillator clock frequency and the 32KHz clock.
The latter is provided by a PMIC on I2C which we don't actually use at
present, but we expect this definition to be used in the kernel and want
to keep our .dts the same.

Signed-off-by: Simon Glass <sjg@chromium.org>
Acked-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Tom Warren <twarren@nvidia.com>