[media] soc_camera/ov2640: Don't use a temp var for an unused value

drivers/media/i2c/soc_camera/ov2640.c:899:32: warning: variable 'win' set but not used [-Wunused-but-set-variable]

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