staging: rtl8723bs: os_dep: remove cast to void pointer

casting to void pointer from any pointer type and vice-versa is done
implicitly and therefore casting is not needed in such a case.

Signed-off-by: Himanshu Jha <himanshujha199640@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>