mips: cdmm: fix use-after-free in mips_cdmm_bus_discover

kfree(dev) has been called inside put_device so anther
kfree would cause a use-after-free bug/

Fixes: 8286ae03 ("MIPS: Add CDMM bus support")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Qinglang Miao <miaoqinglang@huawei.com>
Acked-by: Serge Semin <fancer.lancer@gmail.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>