tegra: dts: Add serial port details

Some Tegra device tree files do not include information about the serial
ports. Add this and also add information about the input clock speed.

The console alias needs to be set up to indicate which port is used for
the console.

Also add a binding file since this is missing.

Series-changes; 5
- Add full serial port nodes from Linux tree (commit fc9d4dbe)
- Use /chosen/stdout-path instead of /aliases/console to specify the console

Signed-off-by: Simon Glass <sjg@chromium.org>