target-riscv: support QMP dump-guest-memory

target-riscv: support QMP dump-guest-memory

Add the support needed for creating prstatus elf notes. This allows
us to use QMP dump-guest-memory.

Now ELF notes of RISC-V only contain prstatus elf notes.

Signed-off-by: Yifei Jiang <jiangyifei@huawei.com>
Signed-off-by: Mingwang Li <limingwang@huawei.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Andrew Jones <drjones@redhat.com>
Reviewed-by: Palmer Dabbelt <palmerdabbelt@google.com>
Message-id: 20210201124458.1248-2-jiangyifei@huawei.com
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>