io_uring/rsrc: avoid NULL check in io_put_rsrc_node()

io_uring/rsrc: avoid NULL check in io_put_rsrc_node()

Most callers of io_put_rsrc_node() already check that node is non-NULL:
- io_rsrc_data_free()
- io_sqe_buffer_register()
- io_reset_rsrc_node()
- io_req_put_rsrc_nodes() (REQ_F_BUF_NODE indicates non-NULL buf_node)

Only io_splice_cleanup() can call io_put_rsrc_node() with a NULL node.
So move the NULL check there.

Signed-off-by: Caleb Sander Mateos <csander@purestorage.com>
Link: https://lore.kernel.org/r/20250216225900.1075446-1-csander@purestorage.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>