ixgbe: Do not decrement budget in ixgbe_clean_rx_irq

This change makes it so that compare the total_rx_packets cleaned to budget
instead of decrementing budget.  The advantage to this approach is that budget
can now be const and we only end up modifying total_rx_packets instead of
modifying both it and budget.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>