drivers/net/phy/mdio_bus.c: call put_device on device_register() failure

It is required to call put_device() if device_register() fails, so that
we give up the last reference to the device.  Calling put_device allows
for mdiobus_release to be executed, kfreeing the bus.

Signed-off-by: Levente Kurusa <levex@linux.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: David Daney <david.daney@cavium.com>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>