i40e: disable MSI-X interrupts if we cannot reserve enough vectors

If we fail on allocating enough MSI-X interrupts, we should disable
them since they were previously enabled in this point of code.

Not disabling them can lead to WARN_ON() being triggered and subsequent
failure in enabling MSI as a fallback; the below message was shown without
this patch while we played with interrupt allocation in i40e driver:

[ 21.461346] sysfs: cannot create duplicate filename '/devices/pci0007:00/0007:00:00.0/0007:01:00.3/msi_irqs'
[ 21.461459] ------------[ cut here ]------------
[ 21.461514] WARNING: CPU: 64 PID: 1155 at fs/sysfs/dir.c:31 sysfs_warn_dup+0x88/0xc0

Also, we noticed that without this patch, if we modprobe the module without
enough MSI-X interrupts (triggering the above warning), unload the module
and re-load it again, we got a crash on the system.
Signed-off-by: Guilherme G Piccoli <gpiccoli@linux.vnet.ibm.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/i40e/i40e_main.c

@@ -7684,6 +7684,7 @@ static int i40e_init_msix(struct i40e_pf *pf)
 		pf->flags &= ~I40E_FLAG_MSIX_ENABLED;
 		kfree(pf->msix_entries);
 		pf->msix_entries = NULL;
+		pci_disable_msix(pf->pdev);
 		return -ENODEV;
 
 	} else if (v_actual == I40E_MIN_MSIX) {