r6040: Fix kmemleak in probe and remove

In the Linux kernel, the following vulnerability has been resolved:

r6040: Fix kmemleak in probe and remove

There is a memory leaks reported by kmemleak:

unreferenced object 0xffff888116111000 (size 2048):
comm "modprobe", pid 817, jiffies 4294759745 (age 76.502s)
hex dump (first 32 bytes):
00 c4 0a 04 81 88 ff ff 08 10 11 16 81 88 ff ff ................
08 10 11 16 81 88 ff ff 00 00 00 00 00 00 00 00 ................
backtrace:
[<ffffffff815bcd82>] kmalloc_trace+0x22/0x60
[<ffffffff827e20ee>] phy_device_create+0x4e/0x90
[<ffffffff827e6072>] get_phy_device+0xd2/0x220
[<ffffffff827e7844>] mdiobus_scan+0xa4/0x2e0
[<ffffffff827e8be2>] __mdiobus_register+0x482/0x8b0
[<ffffffffa01f5d24>] r6040_init_one+0x714/0xd2c [r6040]
...

The problem occurs in probe process as follows:
r6040_init_one:
mdiobus_register
mdiobus_scan <- alloc and register phy_device,
the reference count of phy_device is 3
r6040_mii_probe
phy_connect <- connect to the first phy_device,
so the reference count of the first
phy_device is 4, others are 3
register_netdev <- fault inject succeeded, goto error handling path

// error handling path
err_out_mdio_unregister:
mdiobus_unregister(lp->mii_bus);
err_out_mdio:
mdiobus_free(lp->mii_bus); <- the reference count of the first
phy_device is 1, it is not released
and other phy_devices are released
// similarly, the remove process also has the same problem

The root cause is traced to the phy_device is not disconnected when
removes one r6040 device in r6040_remove_one() or on error handling path
after r6040_mii probed successfully. In r6040_mii_probe(), a net ethernet
device is connected to the first PHY device of mii_bus, in order to
notify the connected driver when the link status changes, which is the
default behavior of the PHY infrastructure to handle everything.
Therefore the phy_device should be disconnected when removes one r6040
device or on error handling path.

Fix it by adding phy_disconnect() when removes one r6040 device or on
error handling path after r6040_mii probed successfully.