rtlwifi: rtl8192cu: Prevent leaking urb

[ Upstream commit 03128643eb5453a798db5770952c73dc64fcaf00 ]

If usb_submit_urb fails the allocated urb should be unanchored and
released.

Signed-off-by: Reto Schneider <code@reto-schneider.ch>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200622132113.14508-3-code@reto-schneider.ch


Signed-off-by: Sasha Levin <sashal@kernel.org>