target/riscv: H extension depends on I extension

Add check for "H depends on an I base integer ISA with 32 x registers"
which is stated at the beginning of chapter 8 of the riscv-privileged
spec(draft-20220717)

Signed-off-by: Weiwei Li <liweiwei@iscas.ac.cn>
Signed-off-by: Junqiang Wang <wangjunqiang@iscas.ac.cn>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Message-Id: <20220718130955.11899-3-liweiwei@iscas.ac.cn>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

target/riscv/cpu.c

@@ -727,6 +727,12 @@ static void riscv_cpu_realize(DeviceState *dev, Error **errp)
             return;
         }
 
+        if (cpu->cfg.ext_h && !cpu->cfg.ext_i) {
+            error_setg(errp,
+                       "H depends on an I base integer ISA with 32 x registers");
+            return;
+        }
+
         if (cpu->cfg.ext_f && !cpu->cfg.ext_icsr) {
             error_setg(errp, "F extension requires Zicsr");
             return;