Pass around CPUArchState instead of using global cpu_single_env.

Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
Acked-by: Richard Henderson <rth@twiddle.net>
Acked-by: Aurelien Jarno <aurelien@aurel32.net>
Acked-by: Guan Xuetao <gxt@mprc.pku.edu.cn>