octeontx-af: fix hardware timestamp configuration

MAC block on CN10K (RPM) supports hardware timestamp configuration. The
previous patch which added timestamp configuration support has a bug.
Though the netdev driver requests to disable timestamp configuration,
the driver is always enabling it.

This patch fixes the same.

Fixes: d1489208 ("octeontx2-af: cn10k: RPM hardware timestamp configuration")
Signed-off-by: Hariprasad Kelam <hkelam@marvell.com>
Signed-off-by: Sunil Goutham <sgoutham@marvell.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: David S. Miller <davem@davemloft.net>