hw/intc/loongarch_ipi: Use MemTxAttrs interface for ipi ops

hw/intc/loongarch_ipi: Use MemTxAttrs interface for ipi ops

There are two interface pairs for MemoryRegionOps, read/write and
read_with_attrs/write_with_attrs. The later is better for ipi device
emulation since initial cpu can be parsed from attrs.requester_id.

And requester_id can be overrided for IOCSR_IPI_SEND and mail_send
function when it is to forward message to another vcpu.

Signed-off-by: Bibo Mao <maobibo@loongson.cn>
Reviewed-by: Song Gao <gaosong@loongson.cn>
Message-Id: <20231215100333.3933632-2-maobibo@loongson.cn>
Signed-off-by: Song Gao <gaosong@loongson.cn>