media: staging: media: meson: remove redundant initialization of mpeg12

The pointer mpeg12 is being initialized however that value is never
read and mpeg12 is being re-assigned almost immediately afterwards.
Remove the redundant initialization.

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Acked-by: Maxime Jourdan <mjourdan@baylibre.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>