qcacld-3.0: Invalid offchannel freq sent in tdls offchannel command

In WMI_TDLS_SET_OFFCHAN_MODE_CMDID the offchannel freq is set to invalid
value due to uninitialized local tdls_channel_switch_params type variable
resulting in fw reading incorrect non zero offchanel freq.

Fix, to zero initialize the local tdls_channel_switch_params variable.

Change-Id: Ia7d6daac098a179a22676620875a2b0d6488a8ad
CRs-Fixed: 2739267