media: meson-ir-tx: remove incorrect doc comment

Do not use kernel-doc "/**" notation when the comment is not in
kernel-doc format. This fixes a sparse warning.

Suggested-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>