hw/loongarch: Add cells missing from uart node

uart node need interrupts and interrupt-parent cells.

Signed-off-by: Song Gao <gaosong@loongson.cn>
Reviewed-by: Bibo Mao <maobibo@loongson.cn>
Message-Id: <20240426091551.2397867-17-gaosong@loongson.cn>
1 file changed