qcacmn: Do not drop the beacon in case of RSN len is less than 2

For security cert TC, RSNIE length can be 1 but if the beacon is
dropped, old entry will remain in scan cache and cause cert TC
failure as connection with old entry with valid RSN IE will pass.

So instead of dropping the frame, do not store the RSN pointer so
that old entry is overwritten.

Change-Id: I2fe4d2dd2352be6850f7a18a2ec829733ded7ee8
CRs-Fixed: 2944120