iavf: Fix the math for valid length for ADq enable

There was a calculation error in virtchnl regarding the valid
length which was fixed recently and a corresponding change needs
to go into the code while we enable ADq.

Signed-off-by: Avinash Dayanand <avinash.dayanand@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/iavf/iavf_virtchnl.c

@@ -983,7 +983,7 @@ void iavf_enable_channels(struct iavf_adapter *adapter)
 		return;
 	}
 
-	len = (adapter->num_tc * sizeof(struct virtchnl_channel_info)) +
+	len = ((adapter->num_tc - 1) * sizeof(struct virtchnl_channel_info)) +
 	       sizeof(struct virtchnl_tc_info);
 
 	vti = kzalloc(len, GFP_KERNEL);