Currently the driver just start the vdev according to the ini
params, without consdering the tx, rx chainmask supported by the
FW per band, per mac, which can lead to connection in 2x2, even
though FW is not capable of 2 antennas on a particular band.
Fix is to intersect both the tx, rx chainmask for both bands,
and change the ini to minimum of the nss supported by ini, and
the BDF setting of the chains.
Change-Id: Ib0e9bac19959bbcf9bade7dbd78674be4099a23d
CRs-Fixed: 2414103