net: mscc: ocelot: Register poll timeout should be wall time not attempts

When doing indirect access in the Ocelot chip, a command is setup,
issued and then we need to poll until the result is ready. The polling
timeout is specified in milliseconds in the datasheet and not in
register access attempts.
It is not a bug on the currently supported platform, but we observed
that the code does not work properly on other platforms that we want to
support as the timing requirements there are different.

Signed-off-by: Steen Hegelund <steen.hegelund@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>