target/arm: Simplify register counting in arm_gen_dynamic_svereg_xml

Rather than increment base_reg and num, compute num from the change
to base_reg at the end.  Clean up some nearby comments.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20230227213329.793795-6-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
1 file changed