media: mtk-vcodec: don't check return val of mtk_venc_get_q_data

The function mtk_venc_get_q_data always returns a reference
so there is no need to check if the return value is null.
In addition move the q_data initialization to the declaration

Signed-off-by: Dafna Hirschfeld <dafna.hirschfeld@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>