net: stmmac: dwmac4_prog_mtl_tx_algorithms() missing write operation

Ported fix from 5.4:
The value of MTL_OPERATION_MODE is not written back.
Add check in ethqos to filter unsupported tx_sched_algorithm.

Signed-off-by: Cheng Han <hancheng2009@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net&gt;.>

Change-Id: I329e00414e0942c542eba7ea1d3b24e450400066
Signed-off-by: Sunil Paidimarri <hisunil@codeaurora.org>