target/riscv: Add basic vmstate description of CPU

target/riscv: Add basic vmstate description of CPU

Add basic CPU state description to the newly created machine.c

Signed-off-by: Yifei Jiang <[email protected]>
Signed-off-by: Yipeng Yin <[email protected]>
Reviewed-by: Alistair Francis <[email protected]>
Message-id: 20201026115530[email protected]
Signed-off-by: Alistair Francis <[email protected]>