[media] media, cx231xx: Fix double free on close

[media] media, cx231xx: Fix double free on close

In cx231xx_v4l2_close() there are two calls to
cx231xx_release_resources(dev) followed by kfree(dev). That is a
problem since cx231xx_release_resources() already kfree()'s its
argument, so we end up doing a double free.

Easily resolved by just removing the redundant kfree() calls after the
calls to cx231xx_release_resources().

I also changed the 'dev = NULL' assignments (which are rather
pointless since 'dev' is about to go out of scope), to 'fh->dev = NULL'
since it looks to me that that is what was actually intended.
And I removed the 'dev = NULL' assignment at the end of
cx231xx_release_resources() since it is pointless.

Signed-off-by: Jesper Juhl <jj@chaosbits.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>