target/riscv: Declare csr_ops[] with a known size

target/riscv: Declare csr_ops[] with a known size

csr_ops[] is currently declared with an unknown size in cpu.h.
Since the array size is known, let's do a complete declaration.

Signed-off-by: Bin Meng <bin.meng@windriver.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-id: 1611024723-14293-1-git-send-email-bmeng.cn@gmail.com
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>