staging: brcm80211: remove code duplication for driver variable lookup

The phy code used its own driver variable lookup functions which were
duplicates of those in the brcmsmac driver (in srom.c). The phy code
now uses the functions in srom.c through the phy_shim interface.

Reviewed-by: Pieter-Paul Giesberts <pieterpg@broadcom.com>
Reviewed-by: Alwin Beukers <alwin@broadcom.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>