cfg80211: Define macro to indicate prev_bssid connect support

Define macro to indicate backport support for prev_bssid
parameter in connect request. This parameter allows the
driver to decide whether to do a new association or a
re-association on a cfg80211 connect request.

Change-Id: I760e2999ec56c9aa0c44ac7b062ee1755192299f
CRs-Fixed: 1004073
Signed-off-by: Vidyullatha Kanchanapally <vidyullatha@codeaurora.org>