Merge branch 'Improvements-to-SJA1105-DSA-RX-timestamping'

Vladimir Oltean says:

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Improvements to SJA1105 DSA RX timestamping

This series makes the sja1105 DSA driver use a dedicated kernel thread
for RX timestamping, a process which is time-sensitive and otherwise a
bit fragile. This allows users to customize their system (probabil an
embedded PTP switch) fully and allocate the CPU bandwidth for the driver
to expedite the RX timestamps as quickly as possible.

While doing this conversion, add a function to the PTP core for
cancelling this kernel thread (function which I found rather strange to
be missing).
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Signed-off-by: David S. Miller <davem@davemloft.net>