staging: octeon-ethernet: rgmii: poll link status on open

Get the initial link status already on open instead of postponing
it to the periodic poll task. This unifies the behaviour with
other interfaces types.

Signed-off-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>