cw1200: use msecs_to_jiffies for conversion

This is only an API consolidation to make things more readable.
Instances of  HZ / CONST  are replaced by appropriate msecs_to_jiffies().

Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>