net: ethernet: am65-cpsw: cleanup TAPRIO handling

Handle offloading commands using switch-case in
am65_cpsw_setup_taprio().

Move checks to am65_cpsw_taprio_replace().

Use NL_SET_ERR_MSG_MOD for error messages.
Change error message from "Failed to set cycle time extension"
to "cycle time extension not supported"

Signed-off-by: Roger Quadros <rogerq@kernel.org>
Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>