target-arm: A64: Implement 2-reg-misc CNT, NOT and RBIT

Implement the 2-reg-misc CNT, NOT and RBIT instructions.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <rth@twiddle.net>
target-arm: A64: Add narrowing 2-reg-misc instructions

Add the narrowing integer instructions in the 2-reg-misc class.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <rth@twiddle.net>