qcacld-3.0: Check vdev handle before returning opmode

The query for an interface opmode returns the opmode
of a particular interface without checking if that
particular virtual interface handle is valid or not.

Fix this by checking the virtual interface handle
before trying to get the operation mode for that
particular interface.

CRs-Fixed: 2572981
Change-Id: I05b5f88455d6374adb41a037d3c5dda905de1497
1 file changed