lib: fdt: Convert fdtdes_setup_mem..() to livetree API

Convert fdtdec_setup_mem_size_base(), get_next_memory_node(),
fdtdec_setup_memory_banksize() and fdtdec_setup_mem_size_base_lowest() to
livetree API.

Tested on ZynqMP zcu104 board.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Simon Glass <sjg@chromium.org>