ixgbe: Drop unnecessary napi_schedule_prep and spare blank line from ixgbe_intr

This patch is a minor cleanup to address the unnecessary use of
napi_schedule_prep in ixgbe_intr and to also remove a blank line that is
not needed since it is separating a comment from the line it is explaining.

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>