MIPS: OCTEON: add missing put_device() call in dwc3_octeon_device_init()

if of_find_device_by_node() succeed, dwc3_octeon_device_init() doesn't have
a corresponding put_device(). Thus add put_device() to fix the exception
handling for this function implementation.

Fixes: 93e502b3

 ("MIPS: OCTEON: Platform support for OCTEON III USB controller")
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>