media: atomisp: Remove unnecessary memset(foo, 0, sizeof(foo)) calls

The memory for all of struct atomisp_video_pipe is kzalloc()-ed in
atomisp_subdev_init() so there is no need to memset parts of
struct atomisp_video_pipe to 0.

Reviewed-by: Andy Shevchenko <andy@kernel.org>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>