[media] media: davinci: vpbe: fix build warning

this patch fixes following build warning
drivers/media/platform/davinci/vpbe_display.c: In function 'vpbe_start_streaming':
drivers/media/platform/davinci/vpbe_display.c:344: warning: unused variable 'vpbe_dev'

Signed-off-by: Lad, Prabhakar <prabhakar.csengg@gmail.com>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>