media: mtk-vcodec: Fix an error handling path in 'mtk_vcodec_probe()'

In case of error the 'media_device_init()' call is not balanced by a
corresponding 'media_device_cleanup()' call.

Add it, when needed, as already done in the remove function.

Fixes: 118add98 ("media: mtk-vcodec: vdec: add media device if using stateless api")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Acked-by: Tzung-Bi Shih <tzungbi@google.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>