V4L/DVB: gspca - gl860: use of real resolutions for MI2020 sensor

- Change of rounded image resolutions to the real ones for MI2020 sensor
  in order to discard 2 random lines in the bottom of images

Signed-off-by: Olivier Lorin <o.lorin@laposte.net>
Signed-off-by: Jean-François Moine <moinejf@free.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>