media: mtk-jpegenc: Fix a compilation issue

‘mtk8195_jpegenc_drvdata’ defined but not used [-Werror=unused-variable]

Signed-off-by: oushixiong <oushixiong@kylinos.cn>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>