media: vim2m: remove unused CLIP macro

The CLIP macro, which was used to clamp color component values to the
[0, 255] range, is no longer used anywhere in the vim2m driver. Remove it
to clean up the code and avoid confusion.

The following issues were reported by checkpatch:
ERROR: Macros with complex values should be enclosed in parentheses

Signed-off-by: Yunseong Kim <ysk@kzalloc.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>