i40e/i40evf: don't lose interrupts

i40e/i40evf: don't lose interrupts

BugLink: http://bugs.launchpad.net/bugs/1547674
While re-enabling interrupts the driver would clear all pending
causes. This meant that if an interrupt was generated while the driver
was cleaning or polling with interrupts disabled, then that interrupt
was lost.  This could cause a queue to become dead, especially for
receive.  Refactored the enable_icr0 function in order to allow
it to be decided by the caller whether the CLEARPBA (clear pending
events) bit will be set while re-enabling the interrupt.

Also update copyright year in file headers.

Change-ID: Ic1db100a05e13c98919057696db147a258ca365a
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
(cherry picked from net-next commit 40d72a50986271e5c30f111e08ebd6d846708bbc)
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>