Use CPURISCVState as argument directly in riscv_cpu_update_mip and
riscv_timer_write_timecmp, since type converts from CPURISCVState to
RISCVCPU in many caller of them and then back to CPURISCVState in them.

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: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Message-Id: <20230309071329.45932-4-liweiwei@iscas.ac.cn>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>