dts: nordic: nrf54h20: Add nodes representing HFXO and LFXO

The HFXO and LFXO oscillators have properties which need to be
specified in the devicetree. These properties are used by clock
controllers, which get these properties from the devicetree.

The BICR also contains these properties. For now, the properties
are duplicated in the bicr node in the devicetree.

Signed-off-by: Andrzej Głąbek <andrzej.glabek@nordicsemi.no>
Signed-off-by: Bjarki Arge Andreasen <bjarki.andreasen@nordicsemi.no>