net: dsa: sja1105: Really make the PTP command read-write

net: dsa: sja1105: Really make the PTP command read-write

When activating tc-taprio offload on the switch ports, the TAS state
machine will try to check whether it is running or not, but will find
both the STARTED and STOPPED bits as false in the
sja1105_tas_check_running function. So the function will return -EINVAL
(an abnormal situation) and the kernel will keep printing this from the
TAS FSM workqueue:

[   37.691971] sja1105 spi0.1: An operation returned -22

The reason is that the underlying function that gets called,
sja1105_ptp_commit, does not actually do a SPI_READ, but a SPI_WRITE. So
the command buffer remains initialized with zeroes instead of retrieving
the hardware state. Fix that.

Fixes: e536c9d2d4e8 ("net: dsa: sja1105: Make the PTP command read-write")
Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>