With recent linux kernels, there is a syscall to probe for various
ISA extensions. These bits were phased in over several kernel
releases, so we still require checks for symbol availability.
Acked-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>