qcacmn: Add a vendor attribute for roam control configuration for full scan

During the roam scan, if there are no desired APs found in the partial
frequency list, an immediate full scan on all the supported frequencies
is initiated as a fallback. This flag controls the frequency list
creation for full scan on the following lines.
1 - Full scan to exclude the frequencies that were already scanned by
    the previous partial scan.
0 - Full scan to include all the supported frequencies irrespective of
    the ones already scanned by partial scan.

Change-Id: Id48ae28e6d0e719b9db9b2e73bd76f9be1ea0b3e
CRs-Fixed: 3343567