media: davinci/vpbe.c: ret contains the return code, not err

Fixes this smatch warning:

drivers/media/platform/davinci/vpbe.c:632 vpbe_initialize() warn: missing error code 'ret'

The function returns 'ret', but instead 'err' was set to -ENOMEM.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Cc: "Lad, Prabhakar" <prabhakar.csengg@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>