media: v4l2-tpg-core.c: add space after %

I know, it's a measly space, but I can't stand it since the
V4L2_PIX_FMT_NV24 case before this case does it right.

So add the space in order to restore blessed symmetry and
consistency and to make the world whole again...

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>