net: mscc: ocelot: ocelot->ts_id_lock and ocelot_port->tx_skbs.lock are IRQ-safe

net: mscc: ocelot: ocelot->ts_id_lock and ocelot_port->tx_skbs.lock are IRQ-safe

ocelot_get_txtstamp() is a threaded IRQ handler, requested explicitly as
such by both ocelot_ptp_rdy_irq_handler() and vsc9959_irq_handler().

As such, it runs with IRQs enabled, and not in hardirq context. Thus,
ocelot_port_add_txtstamp_skb() has no reason to turn off IRQs, it cannot
be preempted by ocelot_get_txtstamp(). For the same reason,
dev_kfree_skb_any_reason() will always evaluate as kfree_skb_reason() in
this calling context, so just simplify the dev_kfree_skb_any() call to
kfree_skb().

Also, ocelot_port_txtstamp_request() runs from NET_TX softirq context,
not with hardirqs enabled. Thus, ocelot_get_txtstamp() which shares the
ocelot_port->tx_skbs.lock lock with it, has no reason to disable hardirqs.

This is part of a larger rework of the TX timestamping procedure.
A logical subportion of the rework has been split into a separate
change.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Link: https://patch.msgid.link/20241205145519.1236778-4-vladimir.oltean@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>