qcacld-3.0: Free HE op element memory for change interface

Currently host driver does not free the memory for HE
operation from cache connection info when it receives change
interface from STA to SAP mode which results in mem leak.

To address above issue, free HE operation element memory on
STA to SAP interface change.

Change-Id: I837640814459a62d819e606fc44adc9bfc60fe5c
CRs-Fixed: 3045848