i40e: remove redundant AQ enable

The admin queue length register is updated in
config_a<sq|rq>_regs functions.  We should not update it again,
as we will trigger firmware to init the AQ again. In this case
firmware will lose the information about the AQ Rx tail position
and will see Rx queue as full (no free desc for FW to use).

Signed-off-by: Kamil Krawczyk <kamil.krawczyk@intel.com>
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: Kavindya Deegala <kavindya.s.deegala@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>