qcacld-2.0: Fix memory leak issue

Memory should be allocated to radar_event only when radar phy
event needs to be sent to WMA layer.

Add changes to fix memory leak.

CRs-Fixed: 1065466
Bug: 34514463
Change-Id: Ia3e93ddd47913956c27487472b6a70eb68d63fd9
Signed-off-by: Ecco Park <eccopark@google.com>