Adds the support for ETF scheduler using TBS feature which is available
in XGMAC and QoS IPs.

Changes from v2:
- Fix checkpatch issues (Jakub)
- Use the TBS bitfield
Signed-off-by: NJose Abreu <Jose.Abreu@synopsys.com>
Signed-off-by: NJakub Kicinski <kuba@kernel.org>