staging: brcm80211: removed void * from softmac phy

Code cleanup. Replacing void * by other pointer types improves code
readability and enforces stronger type checking.

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