qcacld-3.0: Don't consider previous rate flags after vdev restart

Currently rate flags are fetched from adapter before updating new
rate flags. Due to OR condition previous rate flags may not
overwrite and may provide different bandwidth and rate based than
actual params.

Fix is not to consider previous rate flags while updating new rates.

Change-Id: Ic6123858b0560141d1a8f3d366c3c5be95fd2fc9
CRs-Fixed: 2830204