util/cpuinfo-riscv: Support host/cpuinfo.h for riscv

util/cpuinfo-riscv: Support host/cpuinfo.h for riscv

Move detection code out of tcg, similar to other hosts.

Reviewed-by: LIU Zhiwei <zhiwei_liu@linux.alibaba.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>