target/riscv: Fix itrigger when icount is used

When I boot a ubuntu image, QEMU output a "Bad icount read" message and exit.
The reason is that when execute helper_mret or helper_sret, it will
cause a call to icount_get_raw_locked (), which needs set can_do_io flag
on cpustate.

Thus we setting this flag when execute these two instructions.

Signed-off-by: LIU Zhiwei <zhiwei_liu@linux.alibaba.com>
Reviewed-by: Weiwei Li <liweiwei@iscas.ac.cn>
Acked-by: Alistair Francis <alistair.francis@wdc.com>
Message-Id: <20230324064011.976-1-zhiwei_liu@linux.alibaba.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

target/riscv/insn_trans/trans_privileged.c.inc

@@ -77,6 +77,9 @@ static bool trans_sret(DisasContext *ctx, arg_sret *a)
 #ifndef CONFIG_USER_ONLY
     if (has_ext(ctx, RVS)) {
         decode_save_opc(ctx);
+        if (tb_cflags(ctx->base.tb) & CF_USE_ICOUNT) {
+            gen_io_start();
+        }
         gen_helper_sret(cpu_pc, cpu_env);
         tcg_gen_exit_tb(NULL, 0); /* no chaining */
         ctx->base.is_jmp = DISAS_NORETURN;
@@ -93,6 +96,9 @@ static bool trans_mret(DisasContext *ctx, arg_mret *a)
 {
 #ifndef CONFIG_USER_ONLY
     decode_save_opc(ctx);
+    if (tb_cflags(ctx->base.tb) & CF_USE_ICOUNT) {
+        gen_io_start();
+    }
     gen_helper_mret(cpu_pc, cpu_env);
     tcg_gen_exit_tb(NULL, 0); /* no chaining */
     ctx->base.is_jmp = DISAS_NORETURN;