[media] media: soc_camera: don't clear pix->sizeimage in JPEG mode

In JPEG mode, the size of image is variable due to different JPEG compression
rate. We only can get the pix->sizeimage from the user.

If we clear pix->sizeimage in soc_camera_try_fmt() then we will get it from:
	ret = soc_mbus_image_size(xlate->host_fmt, pix->bytesperline,
				pix->height);
	if (ret < 0)
		return ret;

	pix->sizeimage = max_t(u32, pix->sizeimage, ret);

In general, this sizeimage will be larger than the actul JPEG image size.

But vb2 will check the buffer and size of image in __qbuf_userptr():
	/* Check if the provided plane buffer is large enough */
	if (planes[plane].length < q->plane_sizes[plane])

So we shouldn't clear the pix->sizeimage and also shouldn't re-calculate
the pix->sizeimage in soc_mbus_image_size() in JPEG mode

We also shouldn't re-calculate pix->bytesperline:
	ret = soc_mbus_bytes_per_line(pix->width, xlate->host_fmt);
	if (ret < 0)
		return ret;

	pix->bytesperline = max_t(u32, pix->bytesperline, ret);

pix->bytesperline also should be set by the user or by the driver's
try_fmt() implementation.

Change-Id: I700690a2287346127a624b5260922eaa5427a596

Signed-off-by: Albert Wang <twang13@marvell.com>
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>