staging: media: ipu3: remove redundant assignment to pointer css_pipe

Pointer css_pipe is being assigned a value that is never read afterwards.
The assignment is redundant and can be removed.

Cleans up clang scan build warning:
drivers/staging/media/ipu3/ipu3-css.c:2058:3: warning: Value stored
to 'css_pipe' is never read [deadcode.DeadStores]

Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>