net: phy: Fix qca8081 with speeds lower than 2.5Gb/s

A typo in qca808x_read_status means we try to set SMII mode on the port
rather than SGMII when the link speed is not 2.5Gb/s. This results in no
traffic due to the mismatch in configuration between the phy and the
mac.

v2:
 Only change interface mode when the link is up

Fixes: 79c7bc05 ("net: phy: add qca8081 read_status")
Cc: stable@vger.kernel.org
Signed-off-by: Jonathan McDowell <noodles@earth.li>
Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>