staging: brcm80211: make use of crc8 library function

The crc8 function is now available as a library function provided
by kernel module crc8.ko. The function has been removed from brcmutil
module and srom.c now uses crc8 library function.

Reviewed-by: Henry Ptasinski <henryp@broadcom.com>
Reviewed-by: Roland Vossen <rvossen@broadcom.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>