target/riscv: Change the return type of pmp_hart_has_privs() to bool

target/riscv: Change the return type of pmp_hart_has_privs() to bool

We no longer need the pmp_index for matched PMP entry now.

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: <20230517091519.34439-5-liweiwei@iscas.ac.cn>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>