mips: cdmm: Fix refcount leak in mips_cdmm_phys_base

The of_find_compatible_node() function returns a node pointer with
refcount incremented, We should use of_node_put() on it when done
Add the missing of_node_put() to release the refcount.

Fixes: 2121aa3e ("mips: cdmm: Add mti,mips-cdmm dtb node support")
Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
Acked-by: Serge Semin <fancer.lancer@gmail.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>