target/riscv: Fix satp write

These variables should be target_ulong. If truncated to int,
the bool conditions they indicate will be wrong.

As satp is very important for Linux, this bug almost fails every boot.

Signed-off-by: LIU Zhiwei <zhiwei_liu@c-sky.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-id: 20210901124539.222868-1-zhiwei_liu@c-sky.com
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

target/riscv/csr.c

@@ -986,7 +986,7 @@ static RISCVException read_satp(CPURISCVState *env, int csrno,
 static RISCVException write_satp(CPURISCVState *env, int csrno,
                                  target_ulong val)
 {
-    int vm, mask, asid;
+    target_ulong vm, mask, asid;
 
     if (!riscv_feature(env, RISCV_FEATURE_MMU)) {
         return RISCV_EXCP_NONE;