media: bdisp: remove unnecessary IS_ERR() check

The "bdisp->clock" variable cannot be an error pointer here.  No need to
check.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>