[media] V4L: mx3_camera: correct 'sizeimage' value reporting

The 'pix->width' field may be updated in mx3_camera_set_fmt() to
fulfill the IPU stride line alignment requirements. If this update
takes place, the 'fmt.pix.sizeimage' field in the struct v4l2_format
stucture returned by VIDIOC_S_FMT is wrong. We need to update the
'pix->sizeimage' field in the mx3_camera_set_fmt() function to fix
this issue.

Signed-off-by: Anatolij Gustschin <agust@denx.de>
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>