media: imx-jpeg: Identify and handle precision correctly

The decoder will save the precision that was detected from jpeg header
and use it later, when choosing the pixel format and also calculate
bytesperline according to precision.

The 12bit jpeg is not supported yet,
but driver shouldn't led to serious problem if user enqueue a 12 bit jpeg.
And the 12bit jpeg is supported by hardware, driver may support it later.

[hverkuil: document the new precision field]

Signed-off-by: Ming Qian <ming.qian@nxp.com>
Reviewed-by: Mirela Rabulea <mirela.rabulea@nxp.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>