ixgbe: return IXGBE_ERR_RAR_INDEX when out of range

Based on original patch from Shirley Ma <xma@us.ibm.com>
Return IXGBE_ERR_RAR_INDEX when RAR index is out of range, instead of
returning IXGBE_SUCCESS.

CC: Shirley Ma <xma@us.ibm.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Acked-by: Don Skidmore <donald.c.skidmore@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>