ice: enable transmit timestamps for E810 devices

ice: enable transmit timestamps for E810 devices

Add support for enabling Tx timestamp requests for outgoing packets on
E810 devices.

The ice hardware can support multiple outstanding Tx timestamp requests.
When sending a descriptor to hardware, a Tx timestamp request is made by
setting a request bit, and assigning an index that represents which Tx
timestamp index to store the timestamp in.

Hardware makes no effort to synchronize the index use, so it is up to
software to ensure that Tx timestamp indexes are not re-used before the
timestamp is reported back.

To do this, introduce a Tx timestamp tracker which will keep track of
currently in-use indexes.

In the hot path, if a packet has a timestamp request, an index will be
requested from the tracker. Unfortunately, this does require a lock as
the indexes are shared across all queues on a PHY. There are not enough
indexes to reliably assign only 1 to each queue.

For the E810 devices, the timestamp indexes are not shared across PHYs,
so each port can have its own tracking.

Once hardware captures a timestamp, an interrupt is fired. In this
interrupt, trigger a new work item that will figure out which timestamp
was completed, and report the timestamp back to the stack.

This function loops through the Tx timestamp indexes and checks whether
there is now a valid timestamp. If so, it clears the PHY timestamp
indication in the PHY memory, locks and removes the SKB and bit in the
tracker, then reports the timestamp to the stack.

It is possible in some cases that a timestamp request will be initiated
but never completed. This might occur if the packet is dropped by
software or hardware before it reaches the PHY.

Add a task to the periodic work function that will check whether
a timestamp request is more than a few seconds old. If so, the timestamp
index is cleared in the PHY, and the SKB is released.

Just as with Rx timestamps, the Tx timestamps are only 40 bits wide, and
use the same overall logic for extending to 64 bits of nanoseconds.

With this change, E810 devices should be able to perform basic PTP
functionality.

Future changes will extend the support to cover the E822-based devices.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Tony Brelinski <tonyx.brelinski@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>