media: venus: fix use after free in vdec_close

commit a0157b5aa34eb43ec4c5510f9c260bbb03be937e upstream.

There appears to be a possible use after free with vdec_close().
The firmware will add buffer release work to the work queue through
HFI callbacks as a normal part of decoding. Randomly closing the
decoder device from userspace during normal decoding can incur
a read after free for inst.

Fix it by cancelling the work in vdec_close.

Cc: stable@vger.kernel.org
Fixes: af2c3834 ("[media] media: venus: adding core part and helper functions")
Signed-off-by: Dikshita Agarwal <quic_dikshita@quicinc.com>
Acked-by: Vikash Garodia <quic_vgarodia@quicinc.com>
Signed-off-by: Stanimir Varbanov <stanimir.k.varbanov@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>