This patch adds support for decoding 1-src data processing insns,
and the first user, C5.6.40 CLZ (count leading zeroes).

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