ixgbe: make sure per Rx queue is disabled before unmapping the receive buffer

ixgbe: make sure per Rx queue is disabled before unmapping the receive buffer

When disable the Rx logic globally, we would also want to disable the per Rx
queue receive logic by per queue Rx control register RXDCTL so no more DMA is
happening from the packet buffer to the receive buffer associated with the Rx
ring, before we start unmapping Rx ring receive buffer. The hardware may take
max of 100us before the corresponding Rx queue is really disabled. Added
ixgbe_disable_rx_queue() for this purpose.

Signed-off-by: Yi Zou <yi.zou@intel.com>
Tested-by: Stephen Ko <stephen.s.ko@intel.com>
Tested-by: Ross Brattain <ross.b.brattain@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>