rtlwifi: Fix memset argument order

These were found using the following semantic match:
// <smpl>
@@expression E1; type T;@@
* memset(E1, ... * sizeof(T) * ..., ...);
// </smpl>

Also take this opportunity to remove the unnecessary void* casts.

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Tested-by: Larry Finger <Larry.Finger@lwfinger.net>
Acked-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>