net: dsa: bcm_sf2: Fix a possible memory leak in bcm_sf2_mdio_register()

net: dsa: bcm_sf2: Fix a possible memory leak in bcm_sf2_mdio_register()

bcm_sf2_mdio_register() calls of_phy_find_device() and then
phy_device_remove() in a loop to remove existing PHY devices.
of_phy_find_device() eventually calls bus_find_device(), which calls
get_device() on the returned struct device * to increment the refcount.
The current implementation does not decrement the refcount, which causes
memory leak.

This commit adds the missing phy_device_free() call to decrement the
refcount via put_device() to balance the refcount.

Fixes: 771089c2a485 ("net: dsa: bcm_sf2: Ensure that MDIO diversion is used")
Signed-off-by: Joe Hattori <joe@pf.is.s.u-tokyo.ac.jp>
Tested-by: Florian Fainelli <florian.fainelli@broadcom.com>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Link: https://patch.msgid.link/20240806011327.3817861-1-joe@pf.is.s.u-tokyo.ac.jp
Signed-off-by: Jakub Kicinski <kuba@kernel.org>