wireless: drivers: make use of WLAN_EID_VENDOR_SPECIFIC

The include file linux/ieee80211.h contains three definitions for
the same thing in enum ieee80211_eid due to historic changes:

/* Information Element IDs */
enum ieee80211_eid {
    :
    WLAN_EID_WPA = 221,
    WLAN_EID_GENERIC = 221,
    WLAN_EID_VENDOR_SPECIFIC = 221,
    :
};

The standard refers to this as "vendor specific" element so the
other two definitions are better not used. This patch changes the
wireless drivers to use one definition, ie. WLAN_EID_VENDOR_SPECIFIC.

Cc: Jouni Malinen <j@w1.fi>
Cc: Dan Williams <dcbw@redhat.com>
Cc: Larry Finger <Larry.Finger@lwfinger.net>
Acked-by: Kalle Valo <kvalo@qca.qualcomm.com> [ath6kl]
Acked-by: Bing Zhao <bzhao@marvell.com> [mwifiex]
Acked-by: Stanislav Yakovlev <stas.yakovlev@gmail.com> [ipw2x00]
Signed-off-by: Arend van Spriel <arend@broadcom.com>
[change libipw as well]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>