V4L/DVB (3670): Fix typo in comment

This patch fixes a typo in a comment.

Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Oliver Endriss <o.endriss@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>