dts: Add and extend Nordic bindings needed for nRF54H20

Add a set of bindings that will be used in the nRF54H20 SoC definition.
Extend the existing GPIOTE binding with properties needed for this SoC.
Also do a tiny clean-up in the bindings added recently for nRF54L15
(HFXO and LFXO).

Signed-off-by: Grzegorz Swiderski <grzegorz.swiderski@nordicsemi.no>
Signed-off-by: Gerard Marull-Paretas <gerard@teslabs.com>
Signed-off-by: Andrzej Głąbek <andrzej.glabek@nordicsemi.no>