cx88: fix locking of sub-driver operations

cx88: fix locking of sub-driver operations

commit 1fe70e963028f34ba5e32488a7870ff4b410b19b upstream.

The BKL conversion of this driver seems to have gone wrong.
Loading the cx88-blackbird driver deadlocks.

The cause: mpeg_ops::open in the cx2388x blackbird driver acquires the
device lock and calls the sub-driver's request_acquire, which tries to
acquire the lock again.  Fix it by clarifying the semantics of
request_acquire, request_release, advise_acquire, and advise_release:
now all will rely on the caller to acquire the device lock.

Based on work by Ben Hutchings <ben@decadent.org.uk>.

Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=31962
Reported-by: Andi Huber <hobrom@gmx.at>
Tested-by: Andi Huber <hobrom@gmx.at>
Tested-by: Marlon de Boer <marlon@hyves.nl>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>