arm64: dts: mt8173: Add clock controller device nodes

This adds the device nodes providing clocks on the Mediatek MT8173.
These are: topckgen, infracfg, pericfg and apmixedsys. These are
fed by two oscillators also added by this patch.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Reviewed-by: Daniel Kurtz <djkurtz@chromium.org>
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>