staging: brcm80211: change parameter in driver variable lookup

The functions getvar() and getintvar() had to pass the buffer
containing the driver variables. Now they pass the structure
containing this buffer hiding what type of buffer/container
is used for storing the driver variables.

Reviewed-by: Pieter-Paul Giesberts <pieterpg@broadcom.com>
Reviewed-by: Roland Vossen <rvossen@broadcom.com>
Reviewed-by: Alwin Beukers <alwin@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>