cfg80211: Define macro for report better BSS in sched scan

Define macro to indicate backport support to sched scan to report
better BSSs

Change-Id: I32639e615ba5f91ebe29a9a0e37b757eec3c7578
CRs-Fixed: 1112378
Signed-off-by: Vidyullatha Kanchanapally <vidyullatha@codeaurora.org>