ice: periodically kick Tx timestamp interrupt

The E822 hardware for Tx timestamping keeps track of how many
outstanding timestamps are still in the PHY memory block. It will not
generate a new interrupt to the MAC until all of the timestamps in the
region have been read.

If somehow all the available data is not read, but the driver has exited
its interrupt routine already, the PHY will not generate a new interrupt
even if new timestamp data is captured. Because no interrupt is
generated, the driver never processes the timestamp data. This state
results in a permanent failure for all future Tx timestamps.

It is not clear how the driver and hardware could enter this state.
However, if it does, there is currently no recovery mechanism.

Add a recovery mechanism via the periodic PTP work thread which invokes
ice_ptp_periodic_work(). Introduce a new check,
ice_ptp_maybe_trigger_tx_interrupt() which checks the PHY timestamp
ready bitmask. If any bits are set, trigger a software interrupt by
writing to PFINT_OICR.

Once triggered, the main timestamp processing thread will read through
the PHY data and clear the outstanding timestamp data. Once cleared, new
data should trigger interrupts as expected.

This should allow recovery from such a state rather than leaving the
device in a state where we cannot process Tx timestamps.

It is possible that this function checks for timestamp data
simultaneously with the interrupt, and it might trigger additional
unnecessary interrupts. This will cause a small amount of additional
processing.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Karol Kolacinski <karol.kolacinski@intel.com>
Reviewed-by: Andrii Staikov <andrii.staikov@intel.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Tested-by: Pucha Himasekhar Reddy <himasekharx.reddy.pucha@intel.com> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>