net: mscc: ocelot: spell out full "ocelot" name instead of "oc"

This is a cosmetic patch that makes the name of the driver private
variable be used uniformly in ocelot_ace.c as in the rest of the driver.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>