Driver core: Fix cleanup in device_create_vargs().

If device_register() in device_create_vargs() fails, the device
must be cleaned up with put_device() (which is also fine on NULL)
instead of kfree().

Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>