qcacmn: Add NULL check for qdf_dev in init_deinit_free_num_units()

As return of wlan_psoc_get_qdf_dev(), qdf_dev may be
NULL. Add null check in case referencing null.

Change-Id: I7e9bd54e5f4b5260f664bdd4ccee0e4267e2b81e
CRs-Fixed: 2247327
1 file changed