rtlwifi: Redo register save locations

commit b9a758a8c905fc59e783ae91ad645452d877ea88 upstream.

The initial USB driver did not use some register save locations in the
private data storage. To save some memory, a union was used to overlay these
variables with USB I/O components. In an update of the gain-control code,
these register save locations are now needed for USB drivers.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>