[media] v4l: Remove "_ACTUAL" from subdev selection API target definition names

The string "_ACTUAL" does not say anything more about the target names. Drop
it. V4L2 selection API was changed by "V4L: Remove "_ACTIVE" from the
selection target name definitions" by Sylwester Nawrocki. This patch does
the same for the V4L2 subdev API.

Signed-off-by: Sakari Ailus <sakari.ailus@iki.fi>
Acked-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>