igb: check memory allocation failure

Check memory allocation failures and return -ENOMEM in such cases, as
already done for other memory allocations in this function.

This avoids NULL pointers dereference.
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Tested-by: Aaron Brown <aaron.f.brown@intel.com
Acked-by: PJ Waskiewicz <peter.waskiewicz.jr@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/igb/igb_main.c

@@ -3162,6 +3162,8 @@ static int igb_sw_init(struct igb_adapter *adapter)
 	/* Setup and initialize a copy of the hw vlan table array */
 	adapter->shadow_vfta = kcalloc(E1000_VLAN_FILTER_TBL_SIZE, sizeof(u32),
 				       GFP_ATOMIC);
+	if (!adapter->shadow_vfta)
+		return -ENOMEM;
 
 	/* This call may decrease the number of queues */
 	if (igb_init_interrupt_scheme(adapter, true)) {