[nrf fromlist] dts: vendor: nordic: nrf54h20: Add missing property for ppib121

ppib121 node was missing offset that need to be applied when
setting up a connection between DPPI130 and DPPI120.

Signed-off-by: Krzysztof Chruściński <krzysztof.chruscinski@nordicsemi.no>

Upstream PR #: 108512

Author: nordic-krch

dts/vendor/nordic/nrf54h20.dtsi

@@ -885,6 +885,7 @@
 				reg = <0x8ef000 0x1000>;
 				status = "disabled";
 				channels = <8>;
+				offset = <16>;
 			};
 
 			cpuppr_vpr: vpr@908000 {