arm: boot: dts: artpec6: Remove unnecessary interrupt-parent property from sub-nodes

"interrupt-parent" property is declared in root node, so it is global
to all nodes. This property is re-declared in few sub-nodes. To avoid
duplication this property is removed from following sub-nodes:
pmu, amba@0, amba@0/ethernet.

Signed-off-by: Surender Polsani <surenderp@techveda.org>
Acked-by: Niklas Cassel <niklas.cassel@axis.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>