net: ethernet: xilinx: Fix race in the random queue selection

net: ethernet: xilinx: Fix race in the random queue selection

In Axi Ethernet MCDMA configuration with the existing
driver we are hard coding max 16 queues for num_queues
private structure variable it should be user configuriable.

Signed-off-by: Kedareswara rao Appana <appanad@xilinx.com>
Acked-by: Harini Katakam <harinik@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>