i40evf: ethtool RSS fixes

Add an extra check to make sure that the indirection table pointer is
valid before dereferencing it.

Change-ID: I698adbf3daff03081d01f489dc95a9f1ad8b12f1
Reported-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Mitch Williams <mitch.a.williams@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/i40evf/i40evf_ethtool.c

@@ -642,6 +642,7 @@ static int i40evf_get_rxfh(struct net_device *netdev, u32 *indir, u8 *key,
 	if (!indir)
 		return 0;
 
+	if (indir) {
 		for (i = 0, j = 0; i <= I40E_VFQF_HLUT_MAX_INDEX; i++) {
 			hlut_val = rd32(hw, I40E_VFQF_HLUT(i));
 			indir[j++] = hlut_val & 0xff;
@@ -649,6 +650,7 @@ static int i40evf_get_rxfh(struct net_device *netdev, u32 *indir, u8 *key,
 			indir[j++] = (hlut_val >> 16) & 0xff;
 			indir[j++] = (hlut_val >> 24) & 0xff;
 		}
+	}
 	return 0;
 }