media: rcar_vpu: Drop unneeded job_ready

It is not required to implement job_ready().
Since this one is dummy, we can drop it.

Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>