staging: brcm80211: void * cleanup in fullmac

Remove improper usage of void * in dhd_linux.c and dhd_sdio.c

Reported-by: Julian Calaby <julian.calaby@gmail.com>
Reviewed-by: Roland Vossen <rvossen@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>