The machine-level MSIP bits are written by accesses to memory-mapped
control registers. Only use CSR instruction for SSIP and USIP.
There is no effect that using CSR instruction to write MSIP when testing
on unleashed board and QEMU.
Signed-off-by: Zong Li <zong.li@sifive.com>
Reviewed-by: Anup Patel <anup.patel@wdc.com>
