idpf: fix possible vport_config NULL pointer deref in remove

Attempting to remove the driver will cause a crash in cases where
the vport failed to initialize. Following trace is from an instance where
the driver failed during an attempt to create a VF:
[ 1661.543624] idpf 0000:84:00.7: Device HW Reset initiated
[ 1722.923726] idpf 0000:84:00.7: Transaction timed-out (op:1 cookie:2900 vc_op:1 salt:29 timeout:60000ms)
[ 1723.353263] BUG: kernel NULL pointer dereference, address: 0000000000000028
...
[ 1723.358472] RIP: 0010:idpf_remove+0x11c/0x200 [idpf]
...
[ 1723.364973] Call Trace:
[ 1723.365475]  <TASK>
[ 1723.365972]  pci_device_remove+0x42/0xb0
[ 1723.366481]  device_release_driver_internal+0x1a9/0x210
[ 1723.366987]  pci_stop_bus_device+0x6d/0x90
[ 1723.367488]  pci_stop_and_remove_bus_device+0x12/0x20
[ 1723.367971]  pci_iov_remove_virtfn+0xbd/0x120
[ 1723.368309]  sriov_disable+0x34/0xe0
[ 1723.368643]  idpf_sriov_configure+0x58/0x140 [idpf]
[ 1723.368982]  sriov_numvfs_store+0xda/0x1c0

Avoid the NULL pointer dereference by adding NULL pointer check for
vport_config[i], before freeing user_config.q_coalesce.

Fixes: e1e3fec ("idpf: preserve coalescing settings across resets")
Signed-off-by: Emil Tantilov <emil.s.tantilov@intel.com>
Reviewed-by: Chittim Madhu <madhu.chittim@intel.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Tested-by: Samuel Salin <Samuel.salin@intel.com>
Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

Author: etantilov

drivers/net/ethernet/intel/idpf/idpf_main.c

@@ -63,6 +63,8 @@ static void idpf_remove(struct pci_dev *pdev)
 	destroy_workqueue(adapter->vc_event_wq);
 
 	for (i = 0; i < adapter->max_vports; i++) {
+		if (!adapter->vport_config[i])
+			continue;
 		kfree(adapter->vport_config[i]->user_config.q_coalesce);
 		kfree(adapter->vport_config[i]);
 		adapter->vport_config[i] = NULL;