[media] em28xx-v4l: fix video buffer field order reporting in progressive mode

The correct field order in progressive mode is V4L2_FIELD_NONE, not V4L2_FIELD_INTERLACED.

Cc: <stable@vger.kernel.org>
Signed-off-by: Frank Schäfer <fschaefer.oss@googlemail.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>