ixgbe: delete one duplicate marcro definition of IXGBE_MAX_L2A_QUEUES

There is typo in ixgbe.h, two marcro definition of IXGBE_MAX_L2A_QUEUES to 4,
delete one, clear the compiler warning.

Signed-off-by: Ethan Zhao <ethan.zhao@oracle.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>