media: siano: Remove unused structures

These structs are not used in the code, remove them.

This fixes the following cocci warning:

drivers/media/common/siano/smscoreapi.h:1049:4-8: WARNING use flexible-array member instead (https://www.kernel.org/doc/html/latest/process/deprecated.html#zero-length-and-one-element-arrays)
drivers/media/common/siano/smscoreapi.h:1055:4-8: WARNING use flexible-array member instead (https://www.kernel.org/doc/html/latest/process/deprecated.html#zero-length-and-one-element-arrays

)

Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>