media: docs: brainless mass add SPDX headers to all media files

All Documentation files outside the uAPI are all licensed with,
at least, GPL 2.0. So, mark them as such.

The ondes at media/uapi are at least GFDL 1.1+.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
diff --git a/Documentation/media/media.h.rst.exceptions b/Documentation/media/media.h.rst.exceptions
index 684fe9c..9b4c265 100644
--- a/Documentation/media/media.h.rst.exceptions
+++ b/Documentation/media/media.h.rst.exceptions
@@ -1,3 +1,5 @@
+# SPDX-License-Identifier: GPL-2.0
+
 # Ignore header name
 ignore define __LINUX_MEDIA_H