V4L/DVB: media/IR: testing the wrong variable

There is a typo here.  We meant to test "rbuf" instead of "drv".  We
already tested "drv" earlier.

Signed-off-by: Dan Carpenter <error27@gmail.com>
Acked-by: Jarod Wilson <jarod@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>