media: meson: vdec: Add MODULE_FIRMWARE macro

The meson-vdec module loads firmware so add MODULE_FIRMWARE macros to
provide that information via modinfo.

Signed-off-by: Juerg Haefliger <juerg.haefliger@canonical.com>
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>