ixgbe: Pass rx_ring directly in ixgbe_configure_srrctl()

Instead of passing the register index of the corresponding rx_ring and find
the way back to get to corresponding rx_ring in ixgbe_configure_srrctl(),
simplify the function ixgbe_configure_srrctl() by passing the rx_ring into
it. Then the register index for that rx_ring is already available from
rx_ring->reg_idx.

Signed-off-by: Yi Zou <yi.zou@intel.com>
Acked-by: Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>