Opcodes accessing Coprocessor 0 are privileged.
Move the CP0 helpers to sysemu/ and simplify the #ifdef'ry.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20210428170410.479308-28-f4bug@amsat.org>