net: phy: sfp: hwmon: Fix scaling of RX power

The RX power read from the SFP uses units of 0.1uW. This must be
scaled to units of uW for HWMON. This requires a divide by 10, not the
current 100.

With this change in place, sensors(1) and ethtool -m agree:

sff2-isa-0000
Adapter: ISA adapter
in0:          +3.23 V
temp1:        +33.1 C
power1:      270.00 uW
power2:      200.00 uW
curr1:        +0.01 A

        Laser output power                        : 0.2743 mW / -5.62 dBm
        Receiver signal average optical power     : 0.2014 mW / -6.96 dBm

Reported-by: chris.healy@zii.aero
Signed-off-by: NAndrew Lunn <andrew@lunn.ch>
Fixes: 1323061a ("net: phy: sfp: Add HWMON support for module sensors")
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/phy/sfp.c

@@ -517,7 +517,7 @@ static int sfp_hwmon_read_sensor(struct sfp *sfp, int reg, long *value)
 
 static void sfp_hwmon_to_rx_power(long *value)
 {
-	*value = DIV_ROUND_CLOSEST(*value, 100);
+	*value = DIV_ROUND_CLOSEST(*value, 10);
 }
 
 static void sfp_hwmon_calibrate(struct sfp *sfp, unsigned int slope, int offset,