[media] media: blackfin: bfin_capture: improve queue_setup() callback

This patch does the following:
a: returns -EINVAL in case format image size is less
   then current image size.
b: assigns nbuffers to two in case the total of vq->num_buffers
   and nbuffers is less then the number of buffers required by driver.
c: sets the sizes[0] of plane according to the fmt passed or which is
   being set in the device.

Signed-off-by: Lad, Prabhakar <prabhakar.csengg@gmail.com>
Tested-by: Scott Jiang <scott.jiang.linux@gmail.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>