[media] V4L: omap1-camera: fix huge lookup array

Since V4L2_MBUS_FMT_* codes have become large and sparse, they cannot
be used as array indices anymore.

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