tc/taprio: add support for preemptible traffic classes

tc/taprio: add support for preemptible traffic classes

Add support for the same kind of "fp" array argument as in mqprio,
except here we already have some handling for per-tc entries (max-sdu).
We just need to expand that logic such that we also add (and parse) the
FP adminStatus property of each traffic class.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David Ahern <dsahern@kernel.org>