qcacld-3.0: Restrict mode change to FTM mode scenarios

Currently if driver load/unload is in progress or driver is
loaded and mode change to FTM mode is issued from the sys
path, memory leakage occurs during driver unload.

To address this issue, don't change mode if driver is already
loaded or load/unload is in progress.

Change-Id: I09cacaf11d516c62de1a9699547eb01476afdc1f
CRs-Fixed: 3349217