target/riscv: Make the short cut really work in pmp_hart_has_privs

Return the result directly for short cut, since We needn't do the
following check on the PMP entries if there is no PMP rules.

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>
Message-Id: <20230517091519.34439-4-liweiwei@iscas.ac.cn>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

target/riscv/pmp.c

@@ -316,6 +316,7 @@ int pmp_hart_has_privs(CPURISCVState *env, target_ulong addr,
                                        allowed_privs, mode)) {
             ret = MAX_RISCV_PMPS;
         }
+        return ret;
     }
 
     if (size == 0) {