qcacld-3.0: Avoid memory leak when adding a TX pattern

In wma_process_add_periodic_tx_ptrn_ind() the buffer allocated for the
WMI parameter will be leaked if wma_find_vdev_by_addr() fails. To
avoid this, reorder the operations so that the buffer is not allocated
unless wma_find_vdev_by_addr() is successful.

Change-Id: Idbd180dcc1bcae5b71f6a56adcfa3b4a7e2595da
CRs-Fixed: 2371905