media: pwc: remove useless header files

It was originally intended to introduce simple_strtol,
but since commit a081c340 ("[media] pwc: Remove dev_hint
module parameter"), that simple_strtol has been removed,
so in order to prevent disputes, the header file should be removed.

Signed-off-by: Zhang Heng <zhangheng@kylinos.cn>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
[hverkuil: fixed small typos in commit log]