i40evf: propagate interrupt allocation failure

Lower level functions are properly reporting errors, and higher-level
functions are correctly responding to errors, but the errors aren't
actually getting through. Typically, the middle-manager function seems
to want to shield its boss from any bad news.

This change fixes a panic if the driver is unable to enable MSI-X or is
unable to acquire enough vectors.

Change-ID: Ifd5787ce92519a5d97e4b465902db930d97b71a1
Signed-off-by: NMitch Williams <mitch.a.williams@intel.com>
Tested-by: NAndrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: NJeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/i40evf/i40evf_main.c

@@ -1163,7 +1163,7 @@ static int i40evf_set_interrupt_capability(struct i40evf_adapter *adapter)
 	for (vector = 0; vector < v_budget; vector++)
 		adapter->msix_entries[vector].entry = vector;
 
-	i40evf_acquire_msix_vectors(adapter, v_budget);
+	err = i40evf_acquire_msix_vectors(adapter, v_budget);
 
 out:
 	adapter->netdev->real_num_tx_queues = pairs;