ixgbe: Move poll routine in order to improve readability

This change relocates the ixgbe_poll routine so it is right next to the
interrupt routine that schedules and calls it.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Tested-by: Stephen Ko <stephen.s.ko@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>