staging: rtl8188eu: Remove unnecessary pointer cast

Remove unnecessary pointer cast. Issue found using the following Coccinelle semantic patch.

@@
type T;
T e;
identifier x;
@@

* T x = (T)e;

Signed-off-by: Janani Ravichandran <janani.rvchndrn@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>