net: mscc: ocelot: export ocelot_hwstamp_get/set functions

Export ocelot_hwstamp_get/set functions so that DSA driver
is able to reuse them.

Signed-off-by: Yangbo Lu <yangbo.lu@nxp.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>