staging: rtl8192u: remove unnecessary cast

Cast is not needed when calling ieee80211_priv, so remove them.
No functional change in this commit.

Signed-off-by: Tong Zhang <ztong0001@gmail.com>
Link: https://lore.kernel.org/r/20220730033335.74153-3-ztong0001@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>