media: media colorspaces*.rst: rename AdobeRGB to opRGB

Drop all Adobe references and use the official opRGB standard
instead.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Cc: stable@vger.kernel.org
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>