igb: Use irq_synchronize per vector when using MSI-X

Synchronize all IRQs when using MSI-X. Similar to ixgbe.
Issue was reported on e1000e, but the patch is also valid for igb.

CC: Jean Delvare <jdelvare@suse.de>
Signed-off-by: Emil Tantilov <emil.s.tantilov@intel.com>
Tested-by: Jeff Pieper <jeffrey.e.pieper@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>