net: stmmac: tc: Add support for ETF Scheduler using TBS

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: Jose Abreu <Jose.Abreu@synopsys.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>