RISC-V: fix bad use of of_node_put

of_find_node_by_type already calls of_node_put, don't call it again.

Fixes: 94f9bf11 ("RISC-V: Fix of_node_* refcount")
Signed-off-by: Andreas Schwab <schwab@suse.de>
Reviewed-by: Atish Patra <atish.patra@wdc.com>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>