staging: brcm80211: use enum identifiers in srom variable tables

In the srom variable tables fields were identified using string
identifiers. This has been replaced by enumeration identifiers.
Reported-by: NJohannes Berg <johannes@sipsolutions.net>
Reviewed-by: NRoland Vossen <rvossen@broadcom.com>
Reviewed-by: NAlwin Beukers <alwin@broadcom.com>
Signed-off-by: NArend van Spriel <arend@broadcom.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>