net: phy: marvell: Fix double free of hwmon device

The hwmon temperature sensor devices is registered using a devm_hwmon
API call.  The marvell_release() would then manually free the device,
not using a devm_hmon API, resulting in the device being removed
twice, leading to a crash in kernfs_find_ns() during the second
removal.

Remove the manual removal, which makes marvell_release() empty, so
remove it as well.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Fixes: 0b04680f ("phy: marvell: Add support for temperature sensor")
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>