[media] docs-rst: media: Explicitly refer to sub-sampling in scaling documentation

Skipping, which is sometimes used in terminology related to sensors when
referring to sub-sampling is replaced by more suitable sub-sampling
instead. Skipping is retained in a note in parentheses.

Suggested-by: Russell King <[e-mail]>
Acked-by: Laurent Pinchart <[e-mail]>
Signed-off-by: Sakari Ailus <[e-mail]>
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>

Documentation/media/uapi/mediactl/media-types.rst

···
 	  supported scaling ratios is entity-specific and can differ
 	  between the horizontal and vertical directions (in particular
 	  scaling can be supported in one direction only). Binning and
-	  skipping are considered as scaling.
+	  sub-sampling (occasionally also referred to as skipping) are
+	  considered as scaling.
 
     -  ..  row 28