net: txgbe: support TX head write-back mode

net: txgbe: support TX head write-back mode

TX head write-back mode is supported on AML devices. When it is enabled,
the hardware no longer writes the descriptors DD one by one, but write
back pointer of completion descriptor to the head_wb address.

Signed-off-by: Jiawen Wu <jiawenwu@trustnetic.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Link: https://patch.msgid.link/20251023014538.12644-3-jiawenwu@trustnetic.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>