net: phy: xgmiitorgmii: Check read_status results

We're ignoring the result of the attached phy device's read_status().
Return it so we can detect errors.

Signed-off-by: Brandon Maier <brandon.maier@rockwellcollins.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>