ixgbevf: reorder main loop in ixgbe_clean_rx_irq to allow for do/while/continue

This change allows us to go from a loop based on the descriptor to one
primarily based on the budget. The advantage to this is that we can avoid
carrying too many values from one iteration to the next.

CC: Alexander Duyck <alexander.h.duyck@redhat.com>
Signed-off-by: Emil Tantilov <emil.s.tantilov@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>