media: v4l2-subdev.h: keep * together with the type

Having the '*' in the next line separated from the type makes it
hard to see that these functions return a pointer to that type.

Instead, keep it next to the type name so it is clear that it is
a pointer to that type.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>