[media] pvrusb2: use msecs_to_jiffies for conversion

This is only an API consolidation and should make things more readable

Signed-off-by: Nicholas Mc Guire <der.herr@hofr.at>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>