media: vpbe_venc: don't store return codes if they won't be used

Fix those two warnings

drivers/media/platform/davinci/vpbe_venc.c: In function ‘venc_set_ntsc’:
drivers/media/platform/davinci/vpbe_venc.c:230:6: warning: variable ‘val’ set but not used [-Wunused-but-set-variable]
  u32 val;
      ^~~
drivers/media/platform/davinci/vpbe_venc.c: In function ‘venc_sub_dev_init’:
drivers/media/platform/davinci/vpbe_venc.c:611:6: warning: variable ‘err’ set but not used [-Wunused-but-set-variable]
  int err;
      ^~~
  AR      drivers/media/platform/davinci/built-in.a

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>