media: imx-jpeg: use NV12M to represent non contiguous NV12

V4L2_PIX_FMT_NV12 requires num_planes equals to 1,
V4L2_PIX_FMT_NV12M requires num_planes equals to 2.
and mxc-jpeg supports 2 planes for nv12,
so we should use 4L2_PIX_FMT_NV12M instead of V4L2_PIX_FMT_NV12,
otherwise it will confuses gstreamer and prevent encoding and decoding.

Signed-off-by: Ming Qian <ming.qian@nxp.com>
Signed-off-by: Shijie Qin <shijie.qin@nxp.com>
Signed-off-by: Zhou Peng <eagle.zhou@nxp.com>
Reviewed-by: Mirela Rabulea <mirela.rabulea@oss.nxp.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>