media: streamzap: remove unused struct members

[ Upstream commit 4df69e46 ]

These struct members do not serve any purpose.

Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Stable-dep-of: f656cfbc ("media: streamzap: fix race between device disconnection and urb callback")
Signed-off-by: Sasha Levin <sashal@kernel.org>