[media] bdisp: remove unused var

Fix the following warning:

drivers/media/platform/sti/bdisp/bdisp-v4l2.c: In function 'bdisp_register_device':
drivers/media/platform/sti/bdisp/bdisp-v4l2.c:1024:26: warning: variable 'pdev' set but not used [-Wunused-but-set-variable]
  struct platform_device *pdev;

Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>