net: phy: mxl-gpy: fix version reporting

The commit 09ce6b20 ("net: phy: mxl-gpy: add temperature sensor")
will overwrite the return value and the reported version will be wrong.
Fix it.

Fixes: 09ce6b20 ("net: phy: mxl-gpy: add temperature sensor")
Signed-off-by: Michael Walle <michael@walle.cc>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>